[PATCH v2 0/7] vfio: Interrupt eventfd hardening

[PATCH v2 0/7] vfio: Interrupt eventfd hardening

[Alex Williamson]

This series hardens interrupt code relative to eventfd registration
across several vfio bus drivers, ensuring that NULL eventfds cannot
be triggered by users.  Several other more minor issues were discovered
and fixed along the way.

Thanks to Reinette for identifying this latent vulnerability.  Thanks,

Alex

v2:
 * Add R-b from Kevin & Reinette (thanks!)
 * Remove unused hwirqs in 5/ and avoid unnecessary hwirq lookup in
   cleanup and init unwind in 6/

Alex Williamson (7):
  vfio/pci: Disable auto-enable of exclusive INTx IRQ
  vfio/pci: Lock external INTx masking ops
  vfio: Introduce interface to flush virqfd inject workqueue
  vfio/pci: Create persistent INTx handler
  vfio/platform: Disable virqfds on cleanup
  vfio/platform: Create persistent IRQ handlers
  vfio/fsl-mc: Block calling interrupt handler without trigger

 drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c    |   7 +-
 drivers/vfio/pci/vfio_pci_intrs.c         | 176 +++++++++++++---------
 drivers/vfio/platform/vfio_platform_irq.c | 105 +++++++++----
 drivers/vfio/virqfd.c                     |  21 +++
 include/linux/vfio.h                      |   2 +
 5 files changed, 205 insertions(+), 106 deletions(-)

-- 
2.44.0

[PATCH v2 1/7] vfio/pci: Disable auto-enable of exclusive INTx IRQ

[Alex Williamson]

Currently for devices requiring masking at the irqchip for INTx, ie.
devices without DisINTx support, the IRQ is enabled in request_irq()
and subsequently disabled as necessary to align with the masked status
flag.  This presents a window where the interrupt could fire between
these events, resulting in the IRQ incrementing the disable depth twice.
This would be unrecoverable for a user since the masked flag prevents
nested enables through vfio.

Instead, invert the logic using IRQF_NO_AUTOEN such that exclusive INTx
is never auto-enabled, then unmask as required.

Cc: stable@vger.kernel.org
Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci_intrs.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 237beac83809..136101179fcb 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -296,8 +296,15 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
 
 	ctx->trigger = trigger;
 
+	/*
+	 * Devices without DisINTx support require an exclusive interrupt,
+	 * IRQ masking is performed at the IRQ chip.  The masked status is
+	 * protected by vdev->irqlock. Setup the IRQ without auto-enable and
+	 * unmask as necessary below under lock.  DisINTx is unmodified by
+	 * the IRQ configuration and may therefore use auto-enable.
+	 */
 	if (!vdev->pci_2_3)
-		irqflags = 0;
+		irqflags = IRQF_NO_AUTOEN;
 
 	ret = request_irq(pdev->irq, vfio_intx_handler,
 			  irqflags, ctx->name, vdev);
@@ -308,13 +315,9 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
 		return ret;
 	}
 
-	/*
-	 * INTx disable will stick across the new irq setup,
-	 * disable_irq won't.
-	 */
 	spin_lock_irqsave(&vdev->irqlock, flags);
-	if (!vdev->pci_2_3 && ctx->masked)
-		disable_irq_nosync(pdev->irq);
+	if (!vdev->pci_2_3 && !ctx->masked)
+		enable_irq(pdev->irq);
 	spin_unlock_irqrestore(&vdev->irqlock, flags);
 
 	return 0;
-- 
2.44.0

Re: [PATCH v2 1/7] vfio/pci: Disable auto-enable of exclusive INTx IRQ

[Eric Auger]

Hi Alex,

On 3/9/24 00:05, Alex Williamson wrote:
> Currently for devices requiring masking at the irqchip for INTx, ie.
> devices without DisINTx support, the IRQ is enabled in request_irq()
> and subsequently disabled as necessary to align with the masked status
> flag.  This presents a window where the interrupt could fire between
> these events, resulting in the IRQ incrementing the disable depth twice.
> This would be unrecoverable for a user since the masked flag prevents
> nested enables through vfio.
>
> Instead, invert the logic using IRQF_NO_AUTOEN such that exclusive INTx
> is never auto-enabled, then unmask as required.
> Cc: stable@vger.kernel.org
> Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  drivers/vfio/pci/vfio_pci_intrs.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 237beac83809..136101179fcb 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -296,8 +296,15 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
>  
>  	ctx->trigger = trigger;
>  
> +	/*
> +	 * Devices without DisINTx support require an exclusive interrupt,
> +	 * IRQ masking is performed at the IRQ chip.  The masked status is
> +	 * protected by vdev->irqlock. Setup the IRQ without auto-enable and
> +	 * unmask as necessary below under lock.  DisINTx is unmodified by
> +	 * the IRQ configuration and may therefore use auto-enable.
If I remember correctly the main reason why the

vdev->pci_2_3 path is left unchanged is due to the fact the irq may not be exclusive
and setting IRQF_NO_AUTOEN could be wrong in that case. May be worth to
precise in the commit msg or here? Besides Reviewed-by: Eric Auger
<eric.auger@redhat.com> Eric   

> +	 */
>  	if (!vdev->pci_2_3)
> -		irqflags = 0;
> +		irqflags = IRQF_NO_AUTOEN;
>  
>  	ret = request_irq(pdev->irq, vfio_intx_handler,
>  			  irqflags, ctx->name, vdev);
> @@ -308,13 +315,9 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
>  		return ret;
>  	}
>  
> -	/*
> -	 * INTx disable will stick across the new irq setup,
> -	 * disable_irq won't.
> -	 */
>  	spin_lock_irqsave(&vdev->irqlock, flags);
> -	if (!vdev->pci_2_3 && ctx->masked)
> -		disable_irq_nosync(pdev->irq);
> +	if (!vdev->pci_2_3 && !ctx->masked)
> +		enable_irq(pdev->irq);
>  	spin_unlock_irqrestore(&vdev->irqlock, flags);
>  
>  	return 0;

Re: [PATCH v2 1/7] vfio/pci: Disable auto-enable of exclusive INTx IRQ

[Alex Williamson]

On Mon, 11 Mar 2024 08:36:07 +0100
Eric Auger <eric.auger@redhat.com> wrote:

> Hi Alex,
> 
> On 3/9/24 00:05, Alex Williamson wrote:
> > Currently for devices requiring masking at the irqchip for INTx, ie.
> > devices without DisINTx support, the IRQ is enabled in request_irq()
> > and subsequently disabled as necessary to align with the masked status
> > flag.  This presents a window where the interrupt could fire between
> > these events, resulting in the IRQ incrementing the disable depth twice.
> > This would be unrecoverable for a user since the masked flag prevents
> > nested enables through vfio.
> >
> > Instead, invert the logic using IRQF_NO_AUTOEN such that exclusive INTx
> > is never auto-enabled, then unmask as required.
> > Cc: stable@vger.kernel.org
> > Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
> > Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > ---
> >  drivers/vfio/pci/vfio_pci_intrs.c | 17 ++++++++++-------
> >  1 file changed, 10 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> > index 237beac83809..136101179fcb 100644
> > --- a/drivers/vfio/pci/vfio_pci_intrs.c
> > +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> > @@ -296,8 +296,15 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
> >  
> >  	ctx->trigger = trigger;
> >  
> > +	/*
> > +	 * Devices without DisINTx support require an exclusive interrupt,
> > +	 * IRQ masking is performed at the IRQ chip.  The masked status is
> > +	 * protected by vdev->irqlock. Setup the IRQ without auto-enable and
> > +	 * unmask as necessary below under lock.  DisINTx is unmodified by
> > +	 * the IRQ configuration and may therefore use auto-enable.  
> If I remember correctly the main reason why the
> 
> vdev->pci_2_3 path is left unchanged is due to the fact the irq may not be exclusive
> and setting IRQF_NO_AUTOEN could be wrong in that case. May be worth to
> precise in the commit msg or here? Besides Reviewed-by: Eric Auger
> <eric.auger@redhat.com> Eric   

IRQF_SHARED and IRQF_NO_AUTOEN are in fact mutually exclusive.  Even if
we could disable auto-enable, the driver sharing the interrupt could
independently enable it.  But really the basis for using IRQF_SHARED is
that we have device level INTx detection and masking.  The comment here
is only to note that request_irq() doesn't gratuitously clear DisINTx,
so the mask state previously applied through config space of the device
is persistent.  Thanks,

Alex
 
> > +	 */
> >  	if (!vdev->pci_2_3)
> > -		irqflags = 0;
> > +		irqflags = IRQF_NO_AUTOEN;
> >  
> >  	ret = request_irq(pdev->irq, vfio_intx_handler,
> >  			  irqflags, ctx->name, vdev);
> > @@ -308,13 +315,9 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
> >  		return ret;
> >  	}
> >  
> > -	/*
> > -	 * INTx disable will stick across the new irq setup,
> > -	 * disable_irq won't.
> > -	 */
> >  	spin_lock_irqsave(&vdev->irqlock, flags);
> > -	if (!vdev->pci_2_3 && ctx->masked)
> > -		disable_irq_nosync(pdev->irq);
> > +	if (!vdev->pci_2_3 && !ctx->masked)
> > +		enable_irq(pdev->irq);
> >  	spin_unlock_irqrestore(&vdev->irqlock, flags);
> >  
> >  	return 0;  
> 

[PATCH v2 2/7] vfio/pci: Lock external INTx masking ops

[Alex Williamson]

Mask operations through config space changes to DisINTx may race INTx
configuration changes via ioctl.  Create wrappers that add locking for
paths outside of the core interrupt code.

In particular, irq_type is updated holding igate, therefore testing
is_intx() requires holding igate.  For example clearing DisINTx from
config space can otherwise race changes of the interrupt configuration.

This aligns interfaces which may trigger the INTx eventfd into two
camps, one side serialized by igate and the other only enabled while
INTx is configured.  A subsequent patch introduces synchronization for
the latter flows.

Cc: stable@vger.kernel.org
Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
Reported-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci_intrs.c | 34 +++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 136101179fcb..75c85eec21b3 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -99,13 +99,15 @@ static void vfio_send_intx_eventfd(void *opaque, void *unused)
 }
 
 /* Returns true if the INTx vfio_pci_irq_ctx.masked value is changed. */
-bool vfio_pci_intx_mask(struct vfio_pci_core_device *vdev)
+static bool __vfio_pci_intx_mask(struct vfio_pci_core_device *vdev)
 {
 	struct pci_dev *pdev = vdev->pdev;
 	struct vfio_pci_irq_ctx *ctx;
 	unsigned long flags;
 	bool masked_changed = false;
 
+	lockdep_assert_held(&vdev->igate);
+
 	spin_lock_irqsave(&vdev->irqlock, flags);
 
 	/*
@@ -143,6 +145,17 @@ bool vfio_pci_intx_mask(struct vfio_pci_core_device *vdev)
 	return masked_changed;
 }
 
+bool vfio_pci_intx_mask(struct vfio_pci_core_device *vdev)
+{
+	bool mask_changed;
+
+	mutex_lock(&vdev->igate);
+	mask_changed = __vfio_pci_intx_mask(vdev);
+	mutex_unlock(&vdev->igate);
+
+	return mask_changed;
+}
+
 /*
  * If this is triggered by an eventfd, we can't call eventfd_signal
  * or else we'll deadlock on the eventfd wait queue.  Return >0 when
@@ -194,12 +207,21 @@ static int vfio_pci_intx_unmask_handler(void *opaque, void *unused)
 	return ret;
 }
 
-void vfio_pci_intx_unmask(struct vfio_pci_core_device *vdev)
+static void __vfio_pci_intx_unmask(struct vfio_pci_core_device *vdev)
 {
+	lockdep_assert_held(&vdev->igate);
+
 	if (vfio_pci_intx_unmask_handler(vdev, NULL) > 0)
 		vfio_send_intx_eventfd(vdev, NULL);
 }
 
+void vfio_pci_intx_unmask(struct vfio_pci_core_device *vdev)
+{
+	mutex_lock(&vdev->igate);
+	__vfio_pci_intx_unmask(vdev);
+	mutex_unlock(&vdev->igate);
+}
+
 static irqreturn_t vfio_intx_handler(int irq, void *dev_id)
 {
 	struct vfio_pci_core_device *vdev = dev_id;
@@ -563,11 +585,11 @@ static int vfio_pci_set_intx_unmask(struct vfio_pci_core_device *vdev,
 		return -EINVAL;
 
 	if (flags & VFIO_IRQ_SET_DATA_NONE) {
-		vfio_pci_intx_unmask(vdev);
+		__vfio_pci_intx_unmask(vdev);
 	} else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
 		uint8_t unmask = *(uint8_t *)data;
 		if (unmask)
-			vfio_pci_intx_unmask(vdev);
+			__vfio_pci_intx_unmask(vdev);
 	} else if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
 		struct vfio_pci_irq_ctx *ctx = vfio_irq_ctx_get(vdev, 0);
 		int32_t fd = *(int32_t *)data;
@@ -594,11 +616,11 @@ static int vfio_pci_set_intx_mask(struct vfio_pci_core_device *vdev,
 		return -EINVAL;
 
 	if (flags & VFIO_IRQ_SET_DATA_NONE) {
-		vfio_pci_intx_mask(vdev);
+		__vfio_pci_intx_mask(vdev);
 	} else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
 		uint8_t mask = *(uint8_t *)data;
 		if (mask)
-			vfio_pci_intx_mask(vdev);
+			__vfio_pci_intx_mask(vdev);
 	} else if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
 		return -ENOTTY; /* XXX implement me */
 	}
-- 
2.44.0

Re: [PATCH v2 2/7] vfio/pci: Lock external INTx masking ops

[Eric Auger]

On 3/9/24 00:05, Alex Williamson wrote:
> Mask operations through config space changes to DisINTx may race INTx
> configuration changes via ioctl.  Create wrappers that add locking for
> paths outside of the core interrupt code.
>
> In particular, irq_type is updated holding igate, therefore testing
> is_intx() requires holding igate.  For example clearing DisINTx from
> config space can otherwise race changes of the interrupt configuration.
>
> This aligns interfaces which may trigger the INTx eventfd into two
> camps, one side serialized by igate and the other only enabled while
> INTx is configured.  A subsequent patch introduces synchronization for
> the latter flows.
>
> Cc: stable@vger.kernel.org
> Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
> Reported-by: Reinette Chatre <reinette.chatre@intel.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  drivers/vfio/pci/vfio_pci_intrs.c | 34 +++++++++++++++++++++++++------
>  1 file changed, 28 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 136101179fcb..75c85eec21b3 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -99,13 +99,15 @@ static void vfio_send_intx_eventfd(void *opaque, void *unused)
>  }
>  
>  /* Returns true if the INTx vfio_pci_irq_ctx.masked value is changed. */
> -bool vfio_pci_intx_mask(struct vfio_pci_core_device *vdev)
> +static bool __vfio_pci_intx_mask(struct vfio_pci_core_device *vdev)
>  {
>  	struct pci_dev *pdev = vdev->pdev;
>  	struct vfio_pci_irq_ctx *ctx;
>  	unsigned long flags;
>  	bool masked_changed = false;
>  
> +	lockdep_assert_held(&vdev->igate);
> +
>  	spin_lock_irqsave(&vdev->irqlock, flags);
>  
>  	/*
> @@ -143,6 +145,17 @@ bool vfio_pci_intx_mask(struct vfio_pci_core_device *vdev)
>  	return masked_changed;
>  }
>  
> +bool vfio_pci_intx_mask(struct vfio_pci_core_device *vdev)
> +{
> +	bool mask_changed;
> +
> +	mutex_lock(&vdev->igate);
> +	mask_changed = __vfio_pci_intx_mask(vdev);
> +	mutex_unlock(&vdev->igate);
> +
> +	return mask_changed;
> +}
> +
>  /*
>   * If this is triggered by an eventfd, we can't call eventfd_signal
>   * or else we'll deadlock on the eventfd wait queue.  Return >0 when
> @@ -194,12 +207,21 @@ static int vfio_pci_intx_unmask_handler(void *opaque, void *unused)
>  	return ret;
>  }
>  
> -void vfio_pci_intx_unmask(struct vfio_pci_core_device *vdev)
> +static void __vfio_pci_intx_unmask(struct vfio_pci_core_device *vdev)
>  {
> +	lockdep_assert_held(&vdev->igate);
> +
>  	if (vfio_pci_intx_unmask_handler(vdev, NULL) > 0)
>  		vfio_send_intx_eventfd(vdev, NULL);
>  }
>  
> +void vfio_pci_intx_unmask(struct vfio_pci_core_device *vdev)
> +{
> +	mutex_lock(&vdev->igate);
> +	__vfio_pci_intx_unmask(vdev);
> +	mutex_unlock(&vdev->igate);
> +}
> +
>  static irqreturn_t vfio_intx_handler(int irq, void *dev_id)
>  {
>  	struct vfio_pci_core_device *vdev = dev_id;
> @@ -563,11 +585,11 @@ static int vfio_pci_set_intx_unmask(struct vfio_pci_core_device *vdev,
>  		return -EINVAL;
>  
>  	if (flags & VFIO_IRQ_SET_DATA_NONE) {
> -		vfio_pci_intx_unmask(vdev);
> +		__vfio_pci_intx_unmask(vdev);
>  	} else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
>  		uint8_t unmask = *(uint8_t *)data;
>  		if (unmask)
> -			vfio_pci_intx_unmask(vdev);
> +			__vfio_pci_intx_unmask(vdev);
>  	} else if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
>  		struct vfio_pci_irq_ctx *ctx = vfio_irq_ctx_get(vdev, 0);
>  		int32_t fd = *(int32_t *)data;
> @@ -594,11 +616,11 @@ static int vfio_pci_set_intx_mask(struct vfio_pci_core_device *vdev,
>  		return -EINVAL;
>  
>  	if (flags & VFIO_IRQ_SET_DATA_NONE) {
> -		vfio_pci_intx_mask(vdev);
> +		__vfio_pci_intx_mask(vdev);
>  	} else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
>  		uint8_t mask = *(uint8_t *)data;
>  		if (mask)
> -			vfio_pci_intx_mask(vdev);
> +			__vfio_pci_intx_mask(vdev);
>  	} else if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
>  		return -ENOTTY; /* XXX implement me */
>  	}

[PATCH v2 3/7] vfio: Introduce interface to flush virqfd inject workqueue

[Alex Williamson]

In order to synchronize changes that can affect the thread callback,
introduce an interface to force a flush of the inject workqueue.  The
irqfd pointer is only valid under spinlock, but the workqueue cannot
be flushed under spinlock.  Therefore the flush work for the irqfd is
queued under spinlock.  The vfio_irqfd_cleanup_wq workqueue is re-used
for queuing this work such that flushing the workqueue is also ordered
relative to shutdown.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/virqfd.c | 21 +++++++++++++++++++++
 include/linux/vfio.h  |  2 ++
 2 files changed, 23 insertions(+)

diff --git a/drivers/vfio/virqfd.c b/drivers/vfio/virqfd.c
index 29c564b7a6e1..532269133801 100644
--- a/drivers/vfio/virqfd.c
+++ b/drivers/vfio/virqfd.c
@@ -101,6 +101,13 @@ static void virqfd_inject(struct work_struct *work)
 		virqfd->thread(virqfd->opaque, virqfd->data);
 }
 
+static void virqfd_flush_inject(struct work_struct *work)
+{
+	struct virqfd *virqfd = container_of(work, struct virqfd, flush_inject);
+
+	flush_work(&virqfd->inject);
+}
+
 int vfio_virqfd_enable(void *opaque,
 		       int (*handler)(void *, void *),
 		       void (*thread)(void *, void *),
@@ -124,6 +131,7 @@ int vfio_virqfd_enable(void *opaque,
 
 	INIT_WORK(&virqfd->shutdown, virqfd_shutdown);
 	INIT_WORK(&virqfd->inject, virqfd_inject);
+	INIT_WORK(&virqfd->flush_inject, virqfd_flush_inject);
 
 	irqfd = fdget(fd);
 	if (!irqfd.file) {
@@ -213,3 +221,16 @@ void vfio_virqfd_disable(struct virqfd **pvirqfd)
 	flush_workqueue(vfio_irqfd_cleanup_wq);
 }
 EXPORT_SYMBOL_GPL(vfio_virqfd_disable);
+
+void vfio_virqfd_flush_thread(struct virqfd **pvirqfd)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&virqfd_lock, flags);
+	if (*pvirqfd && (*pvirqfd)->thread)
+		queue_work(vfio_irqfd_cleanup_wq, &(*pvirqfd)->flush_inject);
+	spin_unlock_irqrestore(&virqfd_lock, flags);
+
+	flush_workqueue(vfio_irqfd_cleanup_wq);
+}
+EXPORT_SYMBOL_GPL(vfio_virqfd_flush_thread);
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 89b265bc6ec3..8b1a29820409 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -356,6 +356,7 @@ struct virqfd {
 	wait_queue_entry_t		wait;
 	poll_table		pt;
 	struct work_struct	shutdown;
+	struct work_struct	flush_inject;
 	struct virqfd		**pvirqfd;
 };
 
@@ -363,5 +364,6 @@ int vfio_virqfd_enable(void *opaque, int (*handler)(void *, void *),
 		       void (*thread)(void *, void *), void *data,
 		       struct virqfd **pvirqfd, int fd);
 void vfio_virqfd_disable(struct virqfd **pvirqfd);
+void vfio_virqfd_flush_thread(struct virqfd **pvirqfd);
 
 #endif /* VFIO_H */
-- 
2.44.0

Re: [PATCH v2 3/7] vfio: Introduce interface to flush virqfd inject workqueue

[Eric Auger]

On 3/9/24 00:05, Alex Williamson wrote:
> In order to synchronize changes that can affect the thread callback,
> introduce an interface to force a flush of the inject workqueue.  The
> irqfd pointer is only valid under spinlock, but the workqueue cannot
> be flushed under spinlock.  Therefore the flush work for the irqfd is
> queued under spinlock.  The vfio_irqfd_cleanup_wq workqueue is re-used
> for queuing this work such that flushing the workqueue is also ordered
> relative to shutdown.
>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  drivers/vfio/virqfd.c | 21 +++++++++++++++++++++
>  include/linux/vfio.h  |  2 ++
>  2 files changed, 23 insertions(+)
>
> diff --git a/drivers/vfio/virqfd.c b/drivers/vfio/virqfd.c
> index 29c564b7a6e1..532269133801 100644
> --- a/drivers/vfio/virqfd.c
> +++ b/drivers/vfio/virqfd.c
> @@ -101,6 +101,13 @@ static void virqfd_inject(struct work_struct *work)
>  		virqfd->thread(virqfd->opaque, virqfd->data);
>  }
>  
> +static void virqfd_flush_inject(struct work_struct *work)
> +{
> +	struct virqfd *virqfd = container_of(work, struct virqfd, flush_inject);
> +
> +	flush_work(&virqfd->inject);
> +}
> +
>  int vfio_virqfd_enable(void *opaque,
>  		       int (*handler)(void *, void *),
>  		       void (*thread)(void *, void *),
> @@ -124,6 +131,7 @@ int vfio_virqfd_enable(void *opaque,
>  
>  	INIT_WORK(&virqfd->shutdown, virqfd_shutdown);
>  	INIT_WORK(&virqfd->inject, virqfd_inject);
> +	INIT_WORK(&virqfd->flush_inject, virqfd_flush_inject);
>  
>  	irqfd = fdget(fd);
>  	if (!irqfd.file) {
> @@ -213,3 +221,16 @@ void vfio_virqfd_disable(struct virqfd **pvirqfd)
>  	flush_workqueue(vfio_irqfd_cleanup_wq);
>  }
>  EXPORT_SYMBOL_GPL(vfio_virqfd_disable);
> +
> +void vfio_virqfd_flush_thread(struct virqfd **pvirqfd)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&virqfd_lock, flags);
> +	if (*pvirqfd && (*pvirqfd)->thread)
> +		queue_work(vfio_irqfd_cleanup_wq, &(*pvirqfd)->flush_inject);
> +	spin_unlock_irqrestore(&virqfd_lock, flags);
> +
> +	flush_workqueue(vfio_irqfd_cleanup_wq);
> +}
> +EXPORT_SYMBOL_GPL(vfio_virqfd_flush_thread);
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 89b265bc6ec3..8b1a29820409 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -356,6 +356,7 @@ struct virqfd {
>  	wait_queue_entry_t		wait;
>  	poll_table		pt;
>  	struct work_struct	shutdown;
> +	struct work_struct	flush_inject;
>  	struct virqfd		**pvirqfd;
>  };
>  
> @@ -363,5 +364,6 @@ int vfio_virqfd_enable(void *opaque, int (*handler)(void *, void *),
>  		       void (*thread)(void *, void *), void *data,
>  		       struct virqfd **pvirqfd, int fd);
>  void vfio_virqfd_disable(struct virqfd **pvirqfd);
> +void vfio_virqfd_flush_thread(struct virqfd **pvirqfd);
>  
>  #endif /* VFIO_H */

[PATCH v2 4/7] vfio/pci: Create persistent INTx handler

[Alex Williamson]

A vulnerability exists where the eventfd for INTx signaling can be
deconfigured, which unregisters the IRQ handler but still allows
eventfds to be signaled with a NULL context through the SET_IRQS ioctl
or through unmask irqfd if the device interrupt is pending.

Ideally this could be solved with some additional locking; the igate
mutex serializes the ioctl and config space accesses, and the interrupt
handler is unregistered relative to the trigger, but the irqfd path
runs asynchronous to those.  The igate mutex cannot be acquired from the
atomic context of the eventfd wake function.  Disabling the irqfd
relative to the eventfd registration is potentially incompatible with
existing userspace.

As a result, the solution implemented here moves configuration of the
INTx interrupt handler to track the lifetime of the INTx context object
and irq_type configuration, rather than registration of a particular
trigger eventfd.  Synchronization is added between the ioctl path and
eventfd_signal() wrapper such that the eventfd trigger can be
dynamically updated relative to in-flight interrupts or irqfd callbacks.

Cc: stable@vger.kernel.org
Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
Reported-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci_intrs.c | 145 ++++++++++++++++--------------
 1 file changed, 78 insertions(+), 67 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 75c85eec21b3..fb5392b749ff 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -90,11 +90,15 @@ static void vfio_send_intx_eventfd(void *opaque, void *unused)
 
 	if (likely(is_intx(vdev) && !vdev->virq_disabled)) {
 		struct vfio_pci_irq_ctx *ctx;
+		struct eventfd_ctx *trigger;
 
 		ctx = vfio_irq_ctx_get(vdev, 0);
 		if (WARN_ON_ONCE(!ctx))
 			return;
-		eventfd_signal(ctx->trigger);
+
+		trigger = READ_ONCE(ctx->trigger);
+		if (likely(trigger))
+			eventfd_signal(trigger);
 	}
 }
 
@@ -253,100 +257,100 @@ static irqreturn_t vfio_intx_handler(int irq, void *dev_id)
 	return ret;
 }
 
-static int vfio_intx_enable(struct vfio_pci_core_device *vdev)
+static int vfio_intx_enable(struct vfio_pci_core_device *vdev,
+			    struct eventfd_ctx *trigger)
 {
+	struct pci_dev *pdev = vdev->pdev;
 	struct vfio_pci_irq_ctx *ctx;
+	unsigned long irqflags;
+	char *name;
+	int ret;
 
 	if (!is_irq_none(vdev))
 		return -EINVAL;
 
-	if (!vdev->pdev->irq)
+	if (!pdev->irq)
 		return -ENODEV;
 
+	name = kasprintf(GFP_KERNEL_ACCOUNT, "vfio-intx(%s)", pci_name(pdev));
+	if (!name)
+		return -ENOMEM;
+
 	ctx = vfio_irq_ctx_alloc(vdev, 0);
 	if (!ctx)
 		return -ENOMEM;
 
+	ctx->name = name;
+	ctx->trigger = trigger;
+
 	/*
-	 * If the virtual interrupt is masked, restore it.  Devices
-	 * supporting DisINTx can be masked at the hardware level
-	 * here, non-PCI-2.3 devices will have to wait until the
-	 * interrupt is enabled.
+	 * Fill the initial masked state based on virq_disabled.  After
+	 * enable, changing the DisINTx bit in vconfig directly changes INTx
+	 * masking.  igate prevents races during setup, once running masked
+	 * is protected via irqlock.
+	 *
+	 * Devices supporting DisINTx also reflect the current mask state in
+	 * the physical DisINTx bit, which is not affected during IRQ setup.
+	 *
+	 * Devices without DisINTx support require an exclusive interrupt.
+	 * IRQ masking is performed at the IRQ chip.  Again, igate protects
+	 * against races during setup and IRQ handlers and irqfds are not
+	 * yet active, therefore masked is stable and can be used to
+	 * conditionally auto-enable the IRQ.
+	 *
+	 * irq_type must be stable while the IRQ handler is registered,
+	 * therefore it must be set before request_irq().
 	 */
 	ctx->masked = vdev->virq_disabled;
-	if (vdev->pci_2_3)
-		pci_intx(vdev->pdev, !ctx->masked);
+	if (vdev->pci_2_3) {
+		pci_intx(pdev, !ctx->masked);
+		irqflags = IRQF_SHARED;
+	} else {
+		irqflags = ctx->masked ? IRQF_NO_AUTOEN : 0;
+	}
 
 	vdev->irq_type = VFIO_PCI_INTX_IRQ_INDEX;
 
+	ret = request_irq(pdev->irq, vfio_intx_handler,
+			  irqflags, ctx->name, vdev);
+	if (ret) {
+		vdev->irq_type = VFIO_PCI_NUM_IRQS;
+		kfree(name);
+		vfio_irq_ctx_free(vdev, ctx, 0);
+		return ret;
+	}
+
 	return 0;
 }
 
-static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
+static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev,
+				struct eventfd_ctx *trigger)
 {
 	struct pci_dev *pdev = vdev->pdev;
-	unsigned long irqflags = IRQF_SHARED;
 	struct vfio_pci_irq_ctx *ctx;
-	struct eventfd_ctx *trigger;
-	unsigned long flags;
-	int ret;
+	struct eventfd_ctx *old;
 
 	ctx = vfio_irq_ctx_get(vdev, 0);
 	if (WARN_ON_ONCE(!ctx))
 		return -EINVAL;
 
-	if (ctx->trigger) {
-		free_irq(pdev->irq, vdev);
-		kfree(ctx->name);
-		eventfd_ctx_put(ctx->trigger);
-		ctx->trigger = NULL;
-	}
-
-	if (fd < 0) /* Disable only */
-		return 0;
-
-	ctx->name = kasprintf(GFP_KERNEL_ACCOUNT, "vfio-intx(%s)",
-			      pci_name(pdev));
-	if (!ctx->name)
-		return -ENOMEM;
-
-	trigger = eventfd_ctx_fdget(fd);
-	if (IS_ERR(trigger)) {
-		kfree(ctx->name);
-		return PTR_ERR(trigger);
-	}
+	old = ctx->trigger;
 
-	ctx->trigger = trigger;
+	WRITE_ONCE(ctx->trigger, trigger);
 
-	/*
-	 * Devices without DisINTx support require an exclusive interrupt,
-	 * IRQ masking is performed at the IRQ chip.  The masked status is
-	 * protected by vdev->irqlock. Setup the IRQ without auto-enable and
-	 * unmask as necessary below under lock.  DisINTx is unmodified by
-	 * the IRQ configuration and may therefore use auto-enable.
-	 */
-	if (!vdev->pci_2_3)
-		irqflags = IRQF_NO_AUTOEN;
-
-	ret = request_irq(pdev->irq, vfio_intx_handler,
-			  irqflags, ctx->name, vdev);
-	if (ret) {
-		ctx->trigger = NULL;
-		kfree(ctx->name);
-		eventfd_ctx_put(trigger);
-		return ret;
+	/* Releasing an old ctx requires synchronizing in-flight users */
+	if (old) {
+		synchronize_irq(pdev->irq);
+		vfio_virqfd_flush_thread(&ctx->unmask);
+		eventfd_ctx_put(old);
 	}
 
-	spin_lock_irqsave(&vdev->irqlock, flags);
-	if (!vdev->pci_2_3 && !ctx->masked)
-		enable_irq(pdev->irq);
-	spin_unlock_irqrestore(&vdev->irqlock, flags);
-
 	return 0;
 }
 
 static void vfio_intx_disable(struct vfio_pci_core_device *vdev)
 {
+	struct pci_dev *pdev = vdev->pdev;
 	struct vfio_pci_irq_ctx *ctx;
 
 	ctx = vfio_irq_ctx_get(vdev, 0);
@@ -354,10 +358,13 @@ static void vfio_intx_disable(struct vfio_pci_core_device *vdev)
 	if (ctx) {
 		vfio_virqfd_disable(&ctx->unmask);
 		vfio_virqfd_disable(&ctx->mask);
+		free_irq(pdev->irq, vdev);
+		if (ctx->trigger)
+			eventfd_ctx_put(ctx->trigger);
+		kfree(ctx->name);
+		vfio_irq_ctx_free(vdev, ctx, 0);
 	}
-	vfio_intx_set_signal(vdev, -1);
 	vdev->irq_type = VFIO_PCI_NUM_IRQS;
-	vfio_irq_ctx_free(vdev, ctx, 0);
 }
 
 /*
@@ -641,19 +648,23 @@ static int vfio_pci_set_intx_trigger(struct vfio_pci_core_device *vdev,
 		return -EINVAL;
 
 	if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
+		struct eventfd_ctx *trigger = NULL;
 		int32_t fd = *(int32_t *)data;
 		int ret;
 
-		if (is_intx(vdev))
-			return vfio_intx_set_signal(vdev, fd);
+		if (fd >= 0) {
+			trigger = eventfd_ctx_fdget(fd);
+			if (IS_ERR(trigger))
+				return PTR_ERR(trigger);
+		}
 
-		ret = vfio_intx_enable(vdev);
-		if (ret)
-			return ret;
+		if (is_intx(vdev))
+			ret = vfio_intx_set_signal(vdev, trigger);
+		else
+			ret = vfio_intx_enable(vdev, trigger);
 
-		ret = vfio_intx_set_signal(vdev, fd);
-		if (ret)
-			vfio_intx_disable(vdev);
+		if (ret && trigger)
+			eventfd_ctx_put(trigger);
 
 		return ret;
 	}
-- 
2.44.0

Re: [PATCH v2 4/7] vfio/pci: Create persistent INTx handler

[Eric Auger]

On 3/9/24 00:05, Alex Williamson wrote:
> A vulnerability exists where the eventfd for INTx signaling can be
> deconfigured, which unregisters the IRQ handler but still allows
> eventfds to be signaled with a NULL context through the SET_IRQS ioctl
> or through unmask irqfd if the device interrupt is pending.
>
> Ideally this could be solved with some additional locking; the igate
> mutex serializes the ioctl and config space accesses, and the interrupt
> handler is unregistered relative to the trigger, but the irqfd path
> runs asynchronous to those.  The igate mutex cannot be acquired from the
> atomic context of the eventfd wake function.  Disabling the irqfd
> relative to the eventfd registration is potentially incompatible with
> existing userspace.
>
> As a result, the solution implemented here moves configuration of the
> INTx interrupt handler to track the lifetime of the INTx context object
> and irq_type configuration, rather than registration of a particular
> trigger eventfd.  Synchronization is added between the ioctl path and
> eventfd_signal() wrapper such that the eventfd trigger can be
> dynamically updated relative to in-flight interrupts or irqfd callbacks.
>
> Cc: stable@vger.kernel.org
> Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
> Reported-by: Reinette Chatre <reinette.chatre@intel.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  drivers/vfio/pci/vfio_pci_intrs.c | 145 ++++++++++++++++--------------
>  1 file changed, 78 insertions(+), 67 deletions(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 75c85eec21b3..fb5392b749ff 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -90,11 +90,15 @@ static void vfio_send_intx_eventfd(void *opaque, void *unused)
>  
>  	if (likely(is_intx(vdev) && !vdev->virq_disabled)) {
>  		struct vfio_pci_irq_ctx *ctx;
> +		struct eventfd_ctx *trigger;
>  
>  		ctx = vfio_irq_ctx_get(vdev, 0);
>  		if (WARN_ON_ONCE(!ctx))
>  			return;
> -		eventfd_signal(ctx->trigger);
> +
> +		trigger = READ_ONCE(ctx->trigger);
> +		if (likely(trigger))
> +			eventfd_signal(trigger);
>  	}
>  }
>  
> @@ -253,100 +257,100 @@ static irqreturn_t vfio_intx_handler(int irq, void *dev_id)
>  	return ret;
>  }
>  
> -static int vfio_intx_enable(struct vfio_pci_core_device *vdev)
> +static int vfio_intx_enable(struct vfio_pci_core_device *vdev,
> +			    struct eventfd_ctx *trigger)
>  {
> +	struct pci_dev *pdev = vdev->pdev;
>  	struct vfio_pci_irq_ctx *ctx;
> +	unsigned long irqflags;
> +	char *name;
> +	int ret;
>  
>  	if (!is_irq_none(vdev))
>  		return -EINVAL;
>  
> -	if (!vdev->pdev->irq)
> +	if (!pdev->irq)
>  		return -ENODEV;
>  
> +	name = kasprintf(GFP_KERNEL_ACCOUNT, "vfio-intx(%s)", pci_name(pdev));
> +	if (!name)
> +		return -ENOMEM;
> +
>  	ctx = vfio_irq_ctx_alloc(vdev, 0);
>  	if (!ctx)
>  		return -ENOMEM;
>  
> +	ctx->name = name;
> +	ctx->trigger = trigger;
> +
>  	/*
> -	 * If the virtual interrupt is masked, restore it.  Devices
> -	 * supporting DisINTx can be masked at the hardware level
> -	 * here, non-PCI-2.3 devices will have to wait until the
> -	 * interrupt is enabled.
> +	 * Fill the initial masked state based on virq_disabled.  After
> +	 * enable, changing the DisINTx bit in vconfig directly changes INTx
> +	 * masking.  igate prevents races during setup, once running masked
> +	 * is protected via irqlock.
> +	 *
> +	 * Devices supporting DisINTx also reflect the current mask state in
> +	 * the physical DisINTx bit, which is not affected during IRQ setup.
> +	 *
> +	 * Devices without DisINTx support require an exclusive interrupt.
> +	 * IRQ masking is performed at the IRQ chip.  Again, igate protects
> +	 * against races during setup and IRQ handlers and irqfds are not
> +	 * yet active, therefore masked is stable and can be used to
> +	 * conditionally auto-enable the IRQ.
> +	 *
> +	 * irq_type must be stable while the IRQ handler is registered,
> +	 * therefore it must be set before request_irq().
>  	 */
>  	ctx->masked = vdev->virq_disabled;
> -	if (vdev->pci_2_3)
> -		pci_intx(vdev->pdev, !ctx->masked);
> +	if (vdev->pci_2_3) {
> +		pci_intx(pdev, !ctx->masked);
> +		irqflags = IRQF_SHARED;
> +	} else {
> +		irqflags = ctx->masked ? IRQF_NO_AUTOEN : 0;
> +	}
>  
>  	vdev->irq_type = VFIO_PCI_INTX_IRQ_INDEX;
>  
> +	ret = request_irq(pdev->irq, vfio_intx_handler,
> +			  irqflags, ctx->name, vdev);
> +	if (ret) {
> +		vdev->irq_type = VFIO_PCI_NUM_IRQS;
> +		kfree(name);
> +		vfio_irq_ctx_free(vdev, ctx, 0);
> +		return ret;
> +	}
> +
>  	return 0;
>  }
>  
> -static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
> +static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev,
> +				struct eventfd_ctx *trigger)
>  {
>  	struct pci_dev *pdev = vdev->pdev;
> -	unsigned long irqflags = IRQF_SHARED;
>  	struct vfio_pci_irq_ctx *ctx;
> -	struct eventfd_ctx *trigger;
> -	unsigned long flags;
> -	int ret;
> +	struct eventfd_ctx *old;
>  
>  	ctx = vfio_irq_ctx_get(vdev, 0);
>  	if (WARN_ON_ONCE(!ctx))
>  		return -EINVAL;
>  
> -	if (ctx->trigger) {
> -		free_irq(pdev->irq, vdev);
> -		kfree(ctx->name);
> -		eventfd_ctx_put(ctx->trigger);
> -		ctx->trigger = NULL;
> -	}
> -
> -	if (fd < 0) /* Disable only */
> -		return 0;
> -
> -	ctx->name = kasprintf(GFP_KERNEL_ACCOUNT, "vfio-intx(%s)",
> -			      pci_name(pdev));
> -	if (!ctx->name)
> -		return -ENOMEM;
> -
> -	trigger = eventfd_ctx_fdget(fd);
> -	if (IS_ERR(trigger)) {
> -		kfree(ctx->name);
> -		return PTR_ERR(trigger);
> -	}
> +	old = ctx->trigger;
>  
> -	ctx->trigger = trigger;
> +	WRITE_ONCE(ctx->trigger, trigger);
>  
> -	/*
> -	 * Devices without DisINTx support require an exclusive interrupt,
> -	 * IRQ masking is performed at the IRQ chip.  The masked status is
> -	 * protected by vdev->irqlock. Setup the IRQ without auto-enable and
> -	 * unmask as necessary below under lock.  DisINTx is unmodified by
> -	 * the IRQ configuration and may therefore use auto-enable.
> -	 */
> -	if (!vdev->pci_2_3)
> -		irqflags = IRQF_NO_AUTOEN;
> -
> -	ret = request_irq(pdev->irq, vfio_intx_handler,
> -			  irqflags, ctx->name, vdev);
> -	if (ret) {
> -		ctx->trigger = NULL;
> -		kfree(ctx->name);
> -		eventfd_ctx_put(trigger);
> -		return ret;
> +	/* Releasing an old ctx requires synchronizing in-flight users */
> +	if (old) {
> +		synchronize_irq(pdev->irq);
> +		vfio_virqfd_flush_thread(&ctx->unmask);
> +		eventfd_ctx_put(old);
>  	}
>  
> -	spin_lock_irqsave(&vdev->irqlock, flags);
> -	if (!vdev->pci_2_3 && !ctx->masked)
> -		enable_irq(pdev->irq);
> -	spin_unlock_irqrestore(&vdev->irqlock, flags);
> -
>  	return 0;
>  }
>  
>  static void vfio_intx_disable(struct vfio_pci_core_device *vdev)
>  {
> +	struct pci_dev *pdev = vdev->pdev;
>  	struct vfio_pci_irq_ctx *ctx;
>  
>  	ctx = vfio_irq_ctx_get(vdev, 0);
> @@ -354,10 +358,13 @@ static void vfio_intx_disable(struct vfio_pci_core_device *vdev)
>  	if (ctx) {
>  		vfio_virqfd_disable(&ctx->unmask);
>  		vfio_virqfd_disable(&ctx->mask);
> +		free_irq(pdev->irq, vdev);
> +		if (ctx->trigger)
> +			eventfd_ctx_put(ctx->trigger);
> +		kfree(ctx->name);
> +		vfio_irq_ctx_free(vdev, ctx, 0);
>  	}
> -	vfio_intx_set_signal(vdev, -1);
>  	vdev->irq_type = VFIO_PCI_NUM_IRQS;
> -	vfio_irq_ctx_free(vdev, ctx, 0);
>  }
>  
>  /*
> @@ -641,19 +648,23 @@ static int vfio_pci_set_intx_trigger(struct vfio_pci_core_device *vdev,
>  		return -EINVAL;
>  
>  	if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
> +		struct eventfd_ctx *trigger = NULL;
>  		int32_t fd = *(int32_t *)data;
>  		int ret;
>  
> -		if (is_intx(vdev))
> -			return vfio_intx_set_signal(vdev, fd);
> +		if (fd >= 0) {
> +			trigger = eventfd_ctx_fdget(fd);
> +			if (IS_ERR(trigger))
> +				return PTR_ERR(trigger);
> +		}
>  
> -		ret = vfio_intx_enable(vdev);
> -		if (ret)
> -			return ret;
> +		if (is_intx(vdev))
> +			ret = vfio_intx_set_signal(vdev, trigger);
> +		else
> +			ret = vfio_intx_enable(vdev, trigger);
>  
> -		ret = vfio_intx_set_signal(vdev, fd);
> -		if (ret)
> -			vfio_intx_disable(vdev);
> +		if (ret && trigger)
> +			eventfd_ctx_put(trigger);
>  
>  		return ret;
>  	}

[PATCH v2 5/7] vfio/platform: Disable virqfds on cleanup

[Alex Williamson]

irqfds for mask and unmask that are not specifically disabled by the
user are leaked.  Remove any irqfds during cleanup

Cc: Eric Auger <eric.auger@redhat.com>
Cc: stable@vger.kernel.org
Fixes: a7fa7c77cf15 ("vfio/platform: implement IRQ masking/unmasking via an eventfd")
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/platform/vfio_platform_irq.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
index 61a1bfb68ac7..e5dcada9e86c 100644
--- a/drivers/vfio/platform/vfio_platform_irq.c
+++ b/drivers/vfio/platform/vfio_platform_irq.c
@@ -321,8 +321,11 @@ void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
 {
 	int i;
 
-	for (i = 0; i < vdev->num_irqs; i++)
+	for (i = 0; i < vdev->num_irqs; i++) {
+		vfio_virqfd_disable(&vdev->irqs[i].mask);
+		vfio_virqfd_disable(&vdev->irqs[i].unmask);
 		vfio_set_trigger(vdev, i, -1, NULL);
+	}
 
 	vdev->num_irqs = 0;
 	kfree(vdev->irqs);
-- 
2.44.0

RE: [PATCH v2 5/7] vfio/platform: Disable virqfds on cleanup

[Tian, Kevin]

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Saturday, March 9, 2024 7:05 AM
> 
> irqfds for mask and unmask that are not specifically disabled by the
> user are leaked.  Remove any irqfds during cleanup
> 
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: stable@vger.kernel.org
> Fixes: a7fa7c77cf15 ("vfio/platform: implement IRQ masking/unmasking via
> an eventfd")
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>

Re: [PATCH v2 5/7] vfio/platform: Disable virqfds on cleanup

[Eric Auger]

Hi Alex,

On 3/9/24 00:05, Alex Williamson wrote:
> irqfds for mask and unmask that are not specifically disabled by the
> user are leaked.  Remove any irqfds during cleanup
>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: stable@vger.kernel.org
> Fixes: a7fa7c77cf15 ("vfio/platform: implement IRQ masking/unmasking via an eventfd")
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  drivers/vfio/platform/vfio_platform_irq.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
> index 61a1bfb68ac7..e5dcada9e86c 100644
> --- a/drivers/vfio/platform/vfio_platform_irq.c
> +++ b/drivers/vfio/platform/vfio_platform_irq.c
> @@ -321,8 +321,11 @@ void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
>  {
>  	int i;
>  
> -	for (i = 0; i < vdev->num_irqs; i++)
> +	for (i = 0; i < vdev->num_irqs; i++) {
> +		vfio_virqfd_disable(&vdev->irqs[i].mask);
> +		vfio_virqfd_disable(&vdev->irqs[i].unmask);
>  		vfio_set_trigger(vdev, i, -1, NULL);
> +	}
>  
>  	vdev->num_irqs = 0;
>  	kfree(vdev->irqs);

[PATCH v2 6/7] vfio/platform: Create persistent IRQ handlers

[Alex Williamson]

The vfio-platform SET_IRQS ioctl currently allows loopback triggering of
an interrupt before a signaling eventfd has been configured by the user,
which thereby allows a NULL pointer dereference.

Rather than register the IRQ relative to a valid trigger, register all
IRQs in a disabled state in the device open path.  This allows mask
operations on the IRQ to nest within the overall enable state governed
by a valid eventfd signal.  This decouples @masked, protected by the
@locked spinlock from @trigger, protected via the @igate mutex.

In doing so, it's guaranteed that changes to @trigger cannot race the
IRQ handlers because the IRQ handler is synchronously disabled before
modifying the trigger, and loopback triggering of the IRQ via ioctl is
safe due to serialization with trigger changes via igate.

For compatibility, request_irq() failures are maintained to be local to
the SET_IRQS ioctl rather than a fatal error in the open device path.
This allows, for example, a userspace driver with polling mode support
to continue to work regardless of moving the request_irq() call site.
This necessarily blocks all SET_IRQS access to the failed index.

Cc: Eric Auger <eric.auger@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 57f972e2b341 ("vfio/platform: trigger an interrupt via eventfd")
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/platform/vfio_platform_irq.c | 100 +++++++++++++++-------
 1 file changed, 68 insertions(+), 32 deletions(-)

diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
index e5dcada9e86c..ef41ecef83af 100644
--- a/drivers/vfio/platform/vfio_platform_irq.c
+++ b/drivers/vfio/platform/vfio_platform_irq.c
@@ -136,6 +136,16 @@ static int vfio_platform_set_irq_unmask(struct vfio_platform_device *vdev,
 	return 0;
 }
 
+/*
+ * The trigger eventfd is guaranteed valid in the interrupt path
+ * and protected by the igate mutex when triggered via ioctl.
+ */
+static void vfio_send_eventfd(struct vfio_platform_irq *irq_ctx)
+{
+	if (likely(irq_ctx->trigger))
+		eventfd_signal(irq_ctx->trigger);
+}
+
 static irqreturn_t vfio_automasked_irq_handler(int irq, void *dev_id)
 {
 	struct vfio_platform_irq *irq_ctx = dev_id;
@@ -155,7 +165,7 @@ static irqreturn_t vfio_automasked_irq_handler(int irq, void *dev_id)
 	spin_unlock_irqrestore(&irq_ctx->lock, flags);
 
 	if (ret == IRQ_HANDLED)
-		eventfd_signal(irq_ctx->trigger);
+		vfio_send_eventfd(irq_ctx);
 
 	return ret;
 }
@@ -164,52 +174,40 @@ static irqreturn_t vfio_irq_handler(int irq, void *dev_id)
 {
 	struct vfio_platform_irq *irq_ctx = dev_id;
 
-	eventfd_signal(irq_ctx->trigger);
+	vfio_send_eventfd(irq_ctx);
 
 	return IRQ_HANDLED;
 }
 
 static int vfio_set_trigger(struct vfio_platform_device *vdev, int index,
-			    int fd, irq_handler_t handler)
+			    int fd)
 {
 	struct vfio_platform_irq *irq = &vdev->irqs[index];
 	struct eventfd_ctx *trigger;
-	int ret;
 
 	if (irq->trigger) {
-		irq_clear_status_flags(irq->hwirq, IRQ_NOAUTOEN);
-		free_irq(irq->hwirq, irq);
-		kfree(irq->name);
+		disable_irq(irq->hwirq);
 		eventfd_ctx_put(irq->trigger);
 		irq->trigger = NULL;
 	}
 
 	if (fd < 0) /* Disable only */
 		return 0;
-	irq->name = kasprintf(GFP_KERNEL_ACCOUNT, "vfio-irq[%d](%s)",
-			      irq->hwirq, vdev->name);
-	if (!irq->name)
-		return -ENOMEM;
 
 	trigger = eventfd_ctx_fdget(fd);
-	if (IS_ERR(trigger)) {
-		kfree(irq->name);
+	if (IS_ERR(trigger))
 		return PTR_ERR(trigger);
-	}
 
 	irq->trigger = trigger;
 
-	irq_set_status_flags(irq->hwirq, IRQ_NOAUTOEN);
-	ret = request_irq(irq->hwirq, handler, 0, irq->name, irq);
-	if (ret) {
-		kfree(irq->name);
-		eventfd_ctx_put(trigger);
-		irq->trigger = NULL;
-		return ret;
-	}
-
-	if (!irq->masked)
-		enable_irq(irq->hwirq);
+	/*
+	 * irq->masked effectively provides nested disables within the overall
+	 * enable relative to trigger.  Specifically request_irq() is called
+	 * with NO_AUTOEN, therefore the IRQ is initially disabled.  The user
+	 * may only further disable the IRQ with a MASK operations because
+	 * irq->masked is initially false.
+	 */
+	enable_irq(irq->hwirq);
 
 	return 0;
 }
@@ -228,7 +226,7 @@ static int vfio_platform_set_irq_trigger(struct vfio_platform_device *vdev,
 		handler = vfio_irq_handler;
 
 	if (!count && (flags & VFIO_IRQ_SET_DATA_NONE))
-		return vfio_set_trigger(vdev, index, -1, handler);
+		return vfio_set_trigger(vdev, index, -1);
 
 	if (start != 0 || count != 1)
 		return -EINVAL;
@@ -236,7 +234,7 @@ static int vfio_platform_set_irq_trigger(struct vfio_platform_device *vdev,
 	if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
 		int32_t fd = *(int32_t *)data;
 
-		return vfio_set_trigger(vdev, index, fd, handler);
+		return vfio_set_trigger(vdev, index, fd);
 	}
 
 	if (flags & VFIO_IRQ_SET_DATA_NONE) {
@@ -260,6 +258,14 @@ int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
 		    unsigned start, unsigned count, uint32_t flags,
 		    void *data) = NULL;
 
+	/*
+	 * For compatibility, errors from request_irq() are local to the
+	 * SET_IRQS path and reflected in the name pointer.  This allows,
+	 * for example, polling mode fallback for an exclusive IRQ failure.
+	 */
+	if (IS_ERR(vdev->irqs[index].name))
+		return PTR_ERR(vdev->irqs[index].name);
+
 	switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
 	case VFIO_IRQ_SET_ACTION_MASK:
 		func = vfio_platform_set_irq_mask;
@@ -280,7 +286,7 @@ int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
 
 int vfio_platform_irq_init(struct vfio_platform_device *vdev)
 {
-	int cnt = 0, i;
+	int cnt = 0, i, ret = 0;
 
 	while (vdev->get_irq(vdev, cnt) >= 0)
 		cnt++;
@@ -292,29 +298,54 @@ int vfio_platform_irq_init(struct vfio_platform_device *vdev)
 
 	for (i = 0; i < cnt; i++) {
 		int hwirq = vdev->get_irq(vdev, i);
+		irq_handler_t handler = vfio_irq_handler;
 
-		if (hwirq < 0)
+		if (hwirq < 0) {
+			ret = -EINVAL;
 			goto err;
+		}
 
 		spin_lock_init(&vdev->irqs[i].lock);
 
 		vdev->irqs[i].flags = VFIO_IRQ_INFO_EVENTFD;
 
-		if (irq_get_trigger_type(hwirq) & IRQ_TYPE_LEVEL_MASK)
+		if (irq_get_trigger_type(hwirq) & IRQ_TYPE_LEVEL_MASK) {
 			vdev->irqs[i].flags |= VFIO_IRQ_INFO_MASKABLE
 						| VFIO_IRQ_INFO_AUTOMASKED;
+			handler = vfio_automasked_irq_handler;
+		}
 
 		vdev->irqs[i].count = 1;
 		vdev->irqs[i].hwirq = hwirq;
 		vdev->irqs[i].masked = false;
+		vdev->irqs[i].name = kasprintf(GFP_KERNEL_ACCOUNT,
+					       "vfio-irq[%d](%s)", hwirq,
+					       vdev->name);
+		if (!vdev->irqs[i].name) {
+			ret = -ENOMEM;
+			goto err;
+		}
+
+		ret = request_irq(hwirq, handler, IRQF_NO_AUTOEN,
+				  vdev->irqs[i].name, &vdev->irqs[i]);
+		if (ret) {
+			kfree(vdev->irqs[i].name);
+			vdev->irqs[i].name = ERR_PTR(ret);
+		}
 	}
 
 	vdev->num_irqs = cnt;
 
 	return 0;
 err:
+	for (--i; i >= 0; i--) {
+		if (!IS_ERR(vdev->irqs[i].name)) {
+			free_irq(vdev->irqs[i].hwirq, &vdev->irqs[i]);
+			kfree(vdev->irqs[i].name);
+		}
+	}
 	kfree(vdev->irqs);
-	return -EINVAL;
+	return ret;
 }
 
 void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
@@ -324,7 +355,12 @@ void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
 	for (i = 0; i < vdev->num_irqs; i++) {
 		vfio_virqfd_disable(&vdev->irqs[i].mask);
 		vfio_virqfd_disable(&vdev->irqs[i].unmask);
-		vfio_set_trigger(vdev, i, -1, NULL);
+		if (!IS_ERR(vdev->irqs[i].name)) {
+			free_irq(vdev->irqs[i].hwirq, &vdev->irqs[i]);
+			if (vdev->irqs[i].trigger)
+				eventfd_ctx_put(vdev->irqs[i].trigger);
+			kfree(vdev->irqs[i].name);
+		}
 	}
 
 	vdev->num_irqs = 0;
-- 
2.44.0

RE: [PATCH v2 6/7] vfio/platform: Create persistent IRQ handlers

[Tian, Kevin]

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Saturday, March 9, 2024 7:05 AM
> 
> The vfio-platform SET_IRQS ioctl currently allows loopback triggering of
> an interrupt before a signaling eventfd has been configured by the user,
> which thereby allows a NULL pointer dereference.
> 
> Rather than register the IRQ relative to a valid trigger, register all
> IRQs in a disabled state in the device open path.  This allows mask
> operations on the IRQ to nest within the overall enable state governed
> by a valid eventfd signal.  This decouples @masked, protected by the
> @locked spinlock from @trigger, protected via the @igate mutex.
> 
> In doing so, it's guaranteed that changes to @trigger cannot race the
> IRQ handlers because the IRQ handler is synchronously disabled before
> modifying the trigger, and loopback triggering of the IRQ via ioctl is
> safe due to serialization with trigger changes via igate.
> 
> For compatibility, request_irq() failures are maintained to be local to
> the SET_IRQS ioctl rather than a fatal error in the open device path.
> This allows, for example, a userspace driver with polling mode support
> to continue to work regardless of moving the request_irq() call site.
> This necessarily blocks all SET_IRQS access to the failed index.
> 
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: stable@vger.kernel.org
> Fixes: 57f972e2b341 ("vfio/platform: trigger an interrupt via eventfd")
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>

Re: [PATCH v2 6/7] vfio/platform: Create persistent IRQ handlers

[Eric Auger]

Hi Alex,

On 3/9/24 00:05, Alex Williamson wrote:
> The vfio-platform SET_IRQS ioctl currently allows loopback triggering of
> an interrupt before a signaling eventfd has been configured by the user,
> which thereby allows a NULL pointer dereference.
>
> Rather than register the IRQ relative to a valid trigger, register all
> IRQs in a disabled state in the device open path.  This allows mask
> operations on the IRQ to nest within the overall enable state governed
> by a valid eventfd signal.  This decouples @masked, protected by the
> @locked spinlock from @trigger, protected via the @igate mutex.
>
> In doing so, it's guaranteed that changes to @trigger cannot race the
> IRQ handlers because the IRQ handler is synchronously disabled before
> modifying the trigger, and loopback triggering of the IRQ via ioctl is
> safe due to serialization with trigger changes via igate.
>
> For compatibility, request_irq() failures are maintained to be local to
> the SET_IRQS ioctl rather than a fatal error in the open device path.
> This allows, for example, a userspace driver with polling mode support
> to continue to work regardless of moving the request_irq() call site.
> This necessarily blocks all SET_IRQS access to the failed index.
>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: stable@vger.kernel.org
> Fixes: 57f972e2b341 ("vfio/platform: trigger an interrupt via eventfd")
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Eric
> ---
>  drivers/vfio/platform/vfio_platform_irq.c | 100 +++++++++++++++-------
>  1 file changed, 68 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
> index e5dcada9e86c..ef41ecef83af 100644
> --- a/drivers/vfio/platform/vfio_platform_irq.c
> +++ b/drivers/vfio/platform/vfio_platform_irq.c
> @@ -136,6 +136,16 @@ static int vfio_platform_set_irq_unmask(struct vfio_platform_device *vdev,
>  	return 0;
>  }
>  
> +/*
> + * The trigger eventfd is guaranteed valid in the interrupt path
> + * and protected by the igate mutex when triggered via ioctl.
> + */
> +static void vfio_send_eventfd(struct vfio_platform_irq *irq_ctx)
> +{
> +	if (likely(irq_ctx->trigger))
> +		eventfd_signal(irq_ctx->trigger);
> +}
> +
>  static irqreturn_t vfio_automasked_irq_handler(int irq, void *dev_id)
>  {
>  	struct vfio_platform_irq *irq_ctx = dev_id;
> @@ -155,7 +165,7 @@ static irqreturn_t vfio_automasked_irq_handler(int irq, void *dev_id)
>  	spin_unlock_irqrestore(&irq_ctx->lock, flags);
>  
>  	if (ret == IRQ_HANDLED)
> -		eventfd_signal(irq_ctx->trigger);
> +		vfio_send_eventfd(irq_ctx);
>  
>  	return ret;
>  }
> @@ -164,52 +174,40 @@ static irqreturn_t vfio_irq_handler(int irq, void *dev_id)
>  {
>  	struct vfio_platform_irq *irq_ctx = dev_id;
>  
> -	eventfd_signal(irq_ctx->trigger);
> +	vfio_send_eventfd(irq_ctx);
>  
>  	return IRQ_HANDLED;
>  }
>  
>  static int vfio_set_trigger(struct vfio_platform_device *vdev, int index,
> -			    int fd, irq_handler_t handler)
> +			    int fd)
>  {
>  	struct vfio_platform_irq *irq = &vdev->irqs[index];
>  	struct eventfd_ctx *trigger;
> -	int ret;
>  
>  	if (irq->trigger) {
> -		irq_clear_status_flags(irq->hwirq, IRQ_NOAUTOEN);
> -		free_irq(irq->hwirq, irq);
> -		kfree(irq->name);
> +		disable_irq(irq->hwirq);
>  		eventfd_ctx_put(irq->trigger);
>  		irq->trigger = NULL;
>  	}
>  
>  	if (fd < 0) /* Disable only */
>  		return 0;
> -	irq->name = kasprintf(GFP_KERNEL_ACCOUNT, "vfio-irq[%d](%s)",
> -			      irq->hwirq, vdev->name);
> -	if (!irq->name)
> -		return -ENOMEM;
>  
>  	trigger = eventfd_ctx_fdget(fd);
> -	if (IS_ERR(trigger)) {
> -		kfree(irq->name);
> +	if (IS_ERR(trigger))
>  		return PTR_ERR(trigger);
> -	}
>  
>  	irq->trigger = trigger;
>  
> -	irq_set_status_flags(irq->hwirq, IRQ_NOAUTOEN);
> -	ret = request_irq(irq->hwirq, handler, 0, irq->name, irq);
> -	if (ret) {
> -		kfree(irq->name);
> -		eventfd_ctx_put(trigger);
> -		irq->trigger = NULL;
> -		return ret;
> -	}
> -
> -	if (!irq->masked)
> -		enable_irq(irq->hwirq);
> +	/*
> +	 * irq->masked effectively provides nested disables within the overall
> +	 * enable relative to trigger.  Specifically request_irq() is called
> +	 * with NO_AUTOEN, therefore the IRQ is initially disabled.  The user
> +	 * may only further disable the IRQ with a MASK operations because
> +	 * irq->masked is initially false.
> +	 */
> +	enable_irq(irq->hwirq);
>  
>  	return 0;
>  }
> @@ -228,7 +226,7 @@ static int vfio_platform_set_irq_trigger(struct vfio_platform_device *vdev,
>  		handler = vfio_irq_handler;
>  
>  	if (!count && (flags & VFIO_IRQ_SET_DATA_NONE))
> -		return vfio_set_trigger(vdev, index, -1, handler);
> +		return vfio_set_trigger(vdev, index, -1);
>  
>  	if (start != 0 || count != 1)
>  		return -EINVAL;
> @@ -236,7 +234,7 @@ static int vfio_platform_set_irq_trigger(struct vfio_platform_device *vdev,
>  	if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
>  		int32_t fd = *(int32_t *)data;
>  
> -		return vfio_set_trigger(vdev, index, fd, handler);
> +		return vfio_set_trigger(vdev, index, fd);
>  	}
>  
>  	if (flags & VFIO_IRQ_SET_DATA_NONE) {
> @@ -260,6 +258,14 @@ int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
>  		    unsigned start, unsigned count, uint32_t flags,
>  		    void *data) = NULL;
>  
> +	/*
> +	 * For compatibility, errors from request_irq() are local to the
> +	 * SET_IRQS path and reflected in the name pointer.  This allows,
> +	 * for example, polling mode fallback for an exclusive IRQ failure.
> +	 */
> +	if (IS_ERR(vdev->irqs[index].name))
> +		return PTR_ERR(vdev->irqs[index].name);
> +
>  	switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
>  	case VFIO_IRQ_SET_ACTION_MASK:
>  		func = vfio_platform_set_irq_mask;
> @@ -280,7 +286,7 @@ int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
>  
>  int vfio_platform_irq_init(struct vfio_platform_device *vdev)
>  {
> -	int cnt = 0, i;
> +	int cnt = 0, i, ret = 0;
>  
>  	while (vdev->get_irq(vdev, cnt) >= 0)
>  		cnt++;
> @@ -292,29 +298,54 @@ int vfio_platform_irq_init(struct vfio_platform_device *vdev)
>  
>  	for (i = 0; i < cnt; i++) {
>  		int hwirq = vdev->get_irq(vdev, i);
> +		irq_handler_t handler = vfio_irq_handler;
>  
> -		if (hwirq < 0)
> +		if (hwirq < 0) {
> +			ret = -EINVAL;
>  			goto err;
> +		}
>  
>  		spin_lock_init(&vdev->irqs[i].lock);
>  
>  		vdev->irqs[i].flags = VFIO_IRQ_INFO_EVENTFD;
>  
> -		if (irq_get_trigger_type(hwirq) & IRQ_TYPE_LEVEL_MASK)
> +		if (irq_get_trigger_type(hwirq) & IRQ_TYPE_LEVEL_MASK) {
>  			vdev->irqs[i].flags |= VFIO_IRQ_INFO_MASKABLE
>  						| VFIO_IRQ_INFO_AUTOMASKED;
> +			handler = vfio_automasked_irq_handler;
> +		}
>  
>  		vdev->irqs[i].count = 1;
>  		vdev->irqs[i].hwirq = hwirq;
>  		vdev->irqs[i].masked = false;
> +		vdev->irqs[i].name = kasprintf(GFP_KERNEL_ACCOUNT,
> +					       "vfio-irq[%d](%s)", hwirq,
> +					       vdev->name);
> +		if (!vdev->irqs[i].name) {
> +			ret = -ENOMEM;
> +			goto err;
> +		}
> +
> +		ret = request_irq(hwirq, handler, IRQF_NO_AUTOEN,
> +				  vdev->irqs[i].name, &vdev->irqs[i]);
> +		if (ret) {
> +			kfree(vdev->irqs[i].name);
> +			vdev->irqs[i].name = ERR_PTR(ret);
> +		}
>  	}
>  
>  	vdev->num_irqs = cnt;
>  
>  	return 0;
>  err:
> +	for (--i; i >= 0; i--) {
> +		if (!IS_ERR(vdev->irqs[i].name)) {
> +			free_irq(vdev->irqs[i].hwirq, &vdev->irqs[i]);
> +			kfree(vdev->irqs[i].name);
> +		}
> +	}
>  	kfree(vdev->irqs);
> -	return -EINVAL;
> +	return ret;
>  }
>  
>  void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
> @@ -324,7 +355,12 @@ void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
>  	for (i = 0; i < vdev->num_irqs; i++) {
>  		vfio_virqfd_disable(&vdev->irqs[i].mask);
>  		vfio_virqfd_disable(&vdev->irqs[i].unmask);
> -		vfio_set_trigger(vdev, i, -1, NULL);
> +		if (!IS_ERR(vdev->irqs[i].name)) {
> +			free_irq(vdev->irqs[i].hwirq, &vdev->irqs[i]);
> +			if (vdev->irqs[i].trigger)
> +				eventfd_ctx_put(vdev->irqs[i].trigger);
> +			kfree(vdev->irqs[i].name);
> +		}
>  	}
>  
>  	vdev->num_irqs = 0;

Re: [PATCH v2 6/7] vfio/platform: Create persistent IRQ handlers

[Eric Auger]

Hi Alex,

On 3/9/24 00:05, Alex Williamson wrote:
> The vfio-platform SET_IRQS ioctl currently allows loopback triggering of
> an interrupt before a signaling eventfd has been configured by the user,
> which thereby allows a NULL pointer dereference.
>
> Rather than register the IRQ relative to a valid trigger, register all
> IRQs in a disabled state in the device open path.  This allows mask
> operations on the IRQ to nest within the overall enable state governed
> by a valid eventfd signal.  This decouples @masked, protected by the
> @locked spinlock from @trigger, protected via the @igate mutex.
>
> In doing so, it's guaranteed that changes to @trigger cannot race the
> IRQ handlers because the IRQ handler is synchronously disabled before
> modifying the trigger, and loopback triggering of the IRQ via ioctl is
> safe due to serialization with trigger changes via igate.
>
> For compatibility, request_irq() failures are maintained to be local to
> the SET_IRQS ioctl rather than a fatal error in the open device path.
> This allows, for example, a userspace driver with polling mode support
> to continue to work regardless of moving the request_irq() call site.
> This necessarily blocks all SET_IRQS access to the failed index.
>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: stable@vger.kernel.org
> Fixes: 57f972e2b341 ("vfio/platform: trigger an interrupt via eventfd")
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric

> ---
>  drivers/vfio/platform/vfio_platform_irq.c | 100 +++++++++++++++-------
>  1 file changed, 68 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
> index e5dcada9e86c..ef41ecef83af 100644
> --- a/drivers/vfio/platform/vfio_platform_irq.c
> +++ b/drivers/vfio/platform/vfio_platform_irq.c
> @@ -136,6 +136,16 @@ static int vfio_platform_set_irq_unmask(struct vfio_platform_device *vdev,
>  	return 0;
>  }
>  
> +/*
> + * The trigger eventfd is guaranteed valid in the interrupt path
> + * and protected by the igate mutex when triggered via ioctl.
> + */
> +static void vfio_send_eventfd(struct vfio_platform_irq *irq_ctx)
> +{
> +	if (likely(irq_ctx->trigger))
> +		eventfd_signal(irq_ctx->trigger);
> +}
> +
>  static irqreturn_t vfio_automasked_irq_handler(int irq, void *dev_id)
>  {
>  	struct vfio_platform_irq *irq_ctx = dev_id;
> @@ -155,7 +165,7 @@ static irqreturn_t vfio_automasked_irq_handler(int irq, void *dev_id)
>  	spin_unlock_irqrestore(&irq_ctx->lock, flags);
>  
>  	if (ret == IRQ_HANDLED)
> -		eventfd_signal(irq_ctx->trigger);
> +		vfio_send_eventfd(irq_ctx);
>  
>  	return ret;
>  }
> @@ -164,52 +174,40 @@ static irqreturn_t vfio_irq_handler(int irq, void *dev_id)
>  {
>  	struct vfio_platform_irq *irq_ctx = dev_id;
>  
> -	eventfd_signal(irq_ctx->trigger);
> +	vfio_send_eventfd(irq_ctx);
>  
>  	return IRQ_HANDLED;
>  }
>  
>  static int vfio_set_trigger(struct vfio_platform_device *vdev, int index,
> -			    int fd, irq_handler_t handler)
> +			    int fd)
>  {
>  	struct vfio_platform_irq *irq = &vdev->irqs[index];
>  	struct eventfd_ctx *trigger;
> -	int ret;
>  
>  	if (irq->trigger) {
> -		irq_clear_status_flags(irq->hwirq, IRQ_NOAUTOEN);
> -		free_irq(irq->hwirq, irq);
> -		kfree(irq->name);
> +		disable_irq(irq->hwirq);
>  		eventfd_ctx_put(irq->trigger);
>  		irq->trigger = NULL;
>  	}
>  
>  	if (fd < 0) /* Disable only */
>  		return 0;
> -	irq->name = kasprintf(GFP_KERNEL_ACCOUNT, "vfio-irq[%d](%s)",
> -			      irq->hwirq, vdev->name);
> -	if (!irq->name)
> -		return -ENOMEM;
>  
>  	trigger = eventfd_ctx_fdget(fd);
> -	if (IS_ERR(trigger)) {
> -		kfree(irq->name);
> +	if (IS_ERR(trigger))
>  		return PTR_ERR(trigger);
> -	}
>  
>  	irq->trigger = trigger;
>  
> -	irq_set_status_flags(irq->hwirq, IRQ_NOAUTOEN);
> -	ret = request_irq(irq->hwirq, handler, 0, irq->name, irq);
> -	if (ret) {
> -		kfree(irq->name);
> -		eventfd_ctx_put(trigger);
> -		irq->trigger = NULL;
> -		return ret;
> -	}
> -
> -	if (!irq->masked)
> -		enable_irq(irq->hwirq);
> +	/*
> +	 * irq->masked effectively provides nested disables within the overall
> +	 * enable relative to trigger.  Specifically request_irq() is called
> +	 * with NO_AUTOEN, therefore the IRQ is initially disabled.  The user
> +	 * may only further disable the IRQ with a MASK operations because
> +	 * irq->masked is initially false.
> +	 */
> +	enable_irq(irq->hwirq);
>  
>  	return 0;
>  }
> @@ -228,7 +226,7 @@ static int vfio_platform_set_irq_trigger(struct vfio_platform_device *vdev,
>  		handler = vfio_irq_handler;
>  
>  	if (!count && (flags & VFIO_IRQ_SET_DATA_NONE))
> -		return vfio_set_trigger(vdev, index, -1, handler);
> +		return vfio_set_trigger(vdev, index, -1);
>  
>  	if (start != 0 || count != 1)
>  		return -EINVAL;
> @@ -236,7 +234,7 @@ static int vfio_platform_set_irq_trigger(struct vfio_platform_device *vdev,
>  	if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
>  		int32_t fd = *(int32_t *)data;
>  
> -		return vfio_set_trigger(vdev, index, fd, handler);
> +		return vfio_set_trigger(vdev, index, fd);
>  	}
>  
>  	if (flags & VFIO_IRQ_SET_DATA_NONE) {
> @@ -260,6 +258,14 @@ int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
>  		    unsigned start, unsigned count, uint32_t flags,
>  		    void *data) = NULL;
>  
> +	/*
> +	 * For compatibility, errors from request_irq() are local to the
> +	 * SET_IRQS path and reflected in the name pointer.  This allows,
> +	 * for example, polling mode fallback for an exclusive IRQ failure.
> +	 */
> +	if (IS_ERR(vdev->irqs[index].name))
> +		return PTR_ERR(vdev->irqs[index].name);
> +
>  	switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
>  	case VFIO_IRQ_SET_ACTION_MASK:
>  		func = vfio_platform_set_irq_mask;
> @@ -280,7 +286,7 @@ int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
>  
>  int vfio_platform_irq_init(struct vfio_platform_device *vdev)
>  {
> -	int cnt = 0, i;
> +	int cnt = 0, i, ret = 0;
>  
>  	while (vdev->get_irq(vdev, cnt) >= 0)
>  		cnt++;
> @@ -292,29 +298,54 @@ int vfio_platform_irq_init(struct vfio_platform_device *vdev)
>  
>  	for (i = 0; i < cnt; i++) {
>  		int hwirq = vdev->get_irq(vdev, i);
> +		irq_handler_t handler = vfio_irq_handler;
>  
> -		if (hwirq < 0)
> +		if (hwirq < 0) {
> +			ret = -EINVAL;
>  			goto err;
> +		}
>  
>  		spin_lock_init(&vdev->irqs[i].lock);
>  
>  		vdev->irqs[i].flags = VFIO_IRQ_INFO_EVENTFD;
>  
> -		if (irq_get_trigger_type(hwirq) & IRQ_TYPE_LEVEL_MASK)
> +		if (irq_get_trigger_type(hwirq) & IRQ_TYPE_LEVEL_MASK) {
>  			vdev->irqs[i].flags |= VFIO_IRQ_INFO_MASKABLE
>  						| VFIO_IRQ_INFO_AUTOMASKED;
> +			handler = vfio_automasked_irq_handler;
> +		}
>  
>  		vdev->irqs[i].count = 1;
>  		vdev->irqs[i].hwirq = hwirq;
>  		vdev->irqs[i].masked = false;
> +		vdev->irqs[i].name = kasprintf(GFP_KERNEL_ACCOUNT,
> +					       "vfio-irq[%d](%s)", hwirq,
> +					       vdev->name);
> +		if (!vdev->irqs[i].name) {
> +			ret = -ENOMEM;
> +			goto err;
> +		}
> +
> +		ret = request_irq(hwirq, handler, IRQF_NO_AUTOEN,
> +				  vdev->irqs[i].name, &vdev->irqs[i]);
> +		if (ret) {
> +			kfree(vdev->irqs[i].name);
> +			vdev->irqs[i].name = ERR_PTR(ret);
> +		}
>  	}
>  
>  	vdev->num_irqs = cnt;
>  
>  	return 0;
>  err:
> +	for (--i; i >= 0; i--) {
> +		if (!IS_ERR(vdev->irqs[i].name)) {
> +			free_irq(vdev->irqs[i].hwirq, &vdev->irqs[i]);
> +			kfree(vdev->irqs[i].name);
> +		}
> +	}
>  	kfree(vdev->irqs);
> -	return -EINVAL;
> +	return ret;
>  }
>  
>  void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
> @@ -324,7 +355,12 @@ void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
>  	for (i = 0; i < vdev->num_irqs; i++) {
>  		vfio_virqfd_disable(&vdev->irqs[i].mask);
>  		vfio_virqfd_disable(&vdev->irqs[i].unmask);
> -		vfio_set_trigger(vdev, i, -1, NULL);
> +		if (!IS_ERR(vdev->irqs[i].name)) {
> +			free_irq(vdev->irqs[i].hwirq, &vdev->irqs[i]);
> +			if (vdev->irqs[i].trigger)
> +				eventfd_ctx_put(vdev->irqs[i].trigger);
> +			kfree(vdev->irqs[i].name);
> +		}
>  	}
>  
>  	vdev->num_irqs = 0;

[PATCH v2 7/7] vfio/fsl-mc: Block calling interrupt handler without trigger

[Alex Williamson]

The eventfd_ctx trigger pointer of the vfio_fsl_mc_irq object is
initially NULL and may become NULL if the user sets the trigger
eventfd to -1.  The interrupt handler itself is guaranteed that
trigger is always valid between request_irq() and free_irq(), but
the loopback testing mechanisms to invoke the handler function
need to test the trigger.  The triggering and setting ioctl paths
both make use of igate and are therefore mutually exclusive.

The vfio-fsl-mc driver does not make use of irqfds, nor does it
support any sort of masking operations, therefore unlike vfio-pci
and vfio-platform, the flow can remain essentially unchanged.

Cc: Diana Craciun <diana.craciun@oss.nxp.com>
Cc: stable@vger.kernel.org
Fixes: cc0ee20bd969 ("vfio/fsl-mc: trigger an interrupt via eventfd")
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c b/drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c
index d62fbfff20b8..82b2afa9b7e3 100644
--- a/drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c
+++ b/drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c
@@ -141,13 +141,14 @@ static int vfio_fsl_mc_set_irq_trigger(struct vfio_fsl_mc_device *vdev,
 	irq = &vdev->mc_irqs[index];
 
 	if (flags & VFIO_IRQ_SET_DATA_NONE) {
-		vfio_fsl_mc_irq_handler(hwirq, irq);
+		if (irq->trigger)
+			eventfd_signal(irq->trigger);
 
 	} else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
 		u8 trigger = *(u8 *)data;
 
-		if (trigger)
-			vfio_fsl_mc_irq_handler(hwirq, irq);
+		if (trigger && irq->trigger)
+			eventfd_signal(irq->trigger);
 	}
 
 	return 0;
-- 
2.44.0

RE: [PATCH v2 7/7] vfio/fsl-mc: Block calling interrupt handler without trigger

[Tian, Kevin]

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Saturday, March 9, 2024 7:05 AM
> 
> The eventfd_ctx trigger pointer of the vfio_fsl_mc_irq object is
> initially NULL and may become NULL if the user sets the trigger
> eventfd to -1.  The interrupt handler itself is guaranteed that
> trigger is always valid between request_irq() and free_irq(), but
> the loopback testing mechanisms to invoke the handler function
> need to test the trigger.  The triggering and setting ioctl paths
> both make use of igate and are therefore mutually exclusive.
> 
> The vfio-fsl-mc driver does not make use of irqfds, nor does it
> support any sort of masking operations, therefore unlike vfio-pci
> and vfio-platform, the flow can remain essentially unchanged.
> 
> Cc: Diana Craciun <diana.craciun@oss.nxp.com>
> Cc: stable@vger.kernel.org
> Fixes: cc0ee20bd969 ("vfio/fsl-mc: trigger an interrupt via eventfd")
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>

Re: [PATCH v2 7/7] vfio/fsl-mc: Block calling interrupt handler without trigger

[Eric Auger]

Hi Alex,
On 3/9/24 00:05, Alex Williamson wrote:
> The eventfd_ctx trigger pointer of the vfio_fsl_mc_irq object is
> initially NULL and may become NULL if the user sets the trigger
> eventfd to -1.  The interrupt handler itself is guaranteed that
> trigger is always valid between request_irq() and free_irq(), but
> the loopback testing mechanisms to invoke the handler function
> need to test the trigger.  The triggering and setting ioctl paths
> both make use of igate and are therefore mutually exclusive.
>
> The vfio-fsl-mc driver does not make use of irqfds, nor does it
> support any sort of masking operations, therefore unlike vfio-pci
> and vfio-platform, the flow can remain essentially unchanged.
>
> Cc: Diana Craciun <diana.craciun@oss.nxp.com>
> Cc: stable@vger.kernel.org
> Fixes: cc0ee20bd969 ("vfio/fsl-mc: trigger an interrupt via eventfd")
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c b/drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c
> index d62fbfff20b8..82b2afa9b7e3 100644
> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c
> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc_intr.c
> @@ -141,13 +141,14 @@ static int vfio_fsl_mc_set_irq_trigger(struct vfio_fsl_mc_device *vdev,
>  	irq = &vdev->mc_irqs[index];
>  
>  	if (flags & VFIO_IRQ_SET_DATA_NONE) {
> -		vfio_fsl_mc_irq_handler(hwirq, irq);
> +		if (irq->trigger)
> +			eventfd_signal(irq->trigger);
>  
>  	} else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
>  		u8 trigger = *(u8 *)data;
>  
> -		if (trigger)
> -			vfio_fsl_mc_irq_handler(hwirq, irq);
> +		if (trigger && irq->trigger)
> +			eventfd_signal(irq->trigger);
>  	}
>  
>  	return 0;