[PATCH v3 0/4] Add vm_bind param check to ensure no overlap with kbo AS carveout

[PATCH v3 0/4] Add vm_bind param check to ensure no overlap with kbo AS carveout

[Adrián Larumbe]

Just a quick check to make sure user-supplied vm_bind regions aren't
clashing with the region reserved for kernel bo's.

I tried to introduce a similar check for panthor_vm_alloc_va(), to throw
back an error when mappings of kernel bo's against specific addresses fall
within the auto_va region. However that is not possible, since there's one
FW region that must be mapped right at CSF_MCU_SHARED_REGION_START. That
is usually not a problem, since drm_mm_insert_node_in_range() will pick
the next one available.

v3 also comes with an early bind range overflow check for sparse mappings.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
---
Changes in v3:
- Fixed off-by-one error for user va range calculations.
- Added new commit for panthor_vm_prepare_unmap_op_ctx to take a whole operation.
- Added commit with bind range early overflow check.
- Link to v2: https://patch.msgid.link/20260619-vm_bind_checks-v2-0-b51abab35f71@collabora.com

Changes in v2:
- Simplified user VA range with kernel BO range overlap to a single statement.
- Link to v1: https://patch.msgid.link/20260616-vm_bind_checks-v1-0-956198602ae3@collabora.com

To: Boris Brezillon <boris.brezillon@collabora.com>
To: Steven Price <steven.price@arm.com>
To: Liviu Dudau <liviu.dudau@arm.com>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
To: Maxime Ripard <mripard@kernel.org>
To: Thomas Zimmermann <tzimmermann@suse.de>
To: David Airlie <airlied@gmail.com>
To: Simona Vetter <simona@ffwll.ch>
To: Heiko Stuebner <heiko@sntech.de>
To: Grant Likely <grant.likely@linaro.org>
To: Adrián Larumbe <adrian.larumbe@collabora.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org

---
Adrián Larumbe (4):
      drm/panthor: Add vm_bind region with kbo range overlap check
      drm/panthor: Fix comment to reflect actual struct field name
      drm/panthor: Have prepare_unmap_op_ctx receive a whole vm_bind op
      drm/panthor: Check for sparse binding range overflow

 drivers/gpu/drm/panthor/panthor_mmu.c | 42 +++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 9 deletions(-)
---
base-commit: 8fca3d8dbebf8d960dad7b10db3cb4a61139454b
change-id: 20260614-vm_bind_checks-46075ba069a0

Best regards,
--  
Adrián Larumbe <adrian.larumbe@collabora.com>

[PATCH v3 1/4] drm/panthor: Add vm_bind region with kbo range overlap check

[Adrián Larumbe]

When a VM is created, caller has to specify the range of the address space
carve-out set aside for mapping kernel BO's. That means vm_bind mappings of
UM-exposed BO's should not intersect with that region, but at the moment
we're not checking this.

At first, I thought of giving these values to drm_gpuvm_init() through its
reserve_{offset, range} arguments, but it turns out that is meant for VM
address spans that are not managed through the usual drm_gpuvm split/merge
circuit, so storing the end of the user VA range at VM creation time and
doing a quick check in the vm_bind ioctl path was the simplest workaround.

Fixes: tag and reference the relevant sparse binding support commit.
Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 31cc57029c12..94789777aac4 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -310,6 +310,9 @@ struct panthor_vm {
 		u64 end;
 	} kernel_auto_va;
 
+	/** @user_va_range: Upper boundary of VAs VM users can map objects against. */
+	u64 user_va_range;
+
 	/** @as: Address space related fields. */
 	struct {
 		/**
@@ -2893,6 +2896,8 @@ panthor_vm_create(struct panthor_device *ptdev, bool for_mcu,
 		va_range = full_va_range;
 	}
 
+	vm->user_va_range = kernel_va_start;
+
 	mutex_init(&vm->mm_lock);
 	drm_mm_init(&vm->mm, kernel_va_start, kernel_va_size);
 	vm->kernel_auto_va.start = auto_kernel_va_start;
@@ -2981,6 +2986,10 @@ panthor_vm_bind_prepare_op_ctx(struct drm_file *file,
 	if (!IS_ALIGNED(op->va | op->size | op->bo_offset, vm_pgsz))
 		return -EINVAL;
 
+	/* We don't allow mappings that overlap with kbo's reserved range */
+	if (op->va + op->size > vm->user_va_range)
+		return -EINVAL;
+
 	switch (op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) {
 	case DRM_PANTHOR_VM_BIND_OP_TYPE_MAP:
 		if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) {

-- 
2.54.0

[PATCH v3 2/4] drm/panthor: Fix comment to reflect actual struct field name

[Adrián Larumbe]

The mismatch would pop up when building the kernel with W=1.

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 94789777aac4..48aa23573cd6 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -306,7 +306,7 @@ struct panthor_vm {
 		/** @kernel_auto_va.start: Start of the automatic VA-range for kernel BOs. */
 		u64 start;
 
-		/** @kernel_auto_va.size: Size of the automatic VA-range for kernel BOs. */
+		/** @kernel_auto_va.end: End of the automatic VA-range for kernel BOs. */
 		u64 end;
 	} kernel_auto_va;
 

-- 
2.54.0

[PATCH v3 3/4] drm/panthor: Have prepare_unmap_op_ctx receive a whole vm_bind op

[Adrián Larumbe]

This change was already enforced for panthor_vm_prepare_map_op_ctx. In a
future commit, access to the drm_panthor_vm_bind_op flags will be needed
inside panthor_vm_prepare_unmap_op_ctx, so rather than expanding the
parameter list, simply pass the operation struct instead.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 48aa23573cd6..77fdad4e5166 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -1416,24 +1416,24 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
 
 static int panthor_vm_prepare_unmap_op_ctx(struct panthor_vm_op_ctx *op_ctx,
 					   struct panthor_vm *vm,
-					   u64 va, u64 size)
+					   const struct drm_panthor_vm_bind_op *op)
 {
 	u32 pt_count = 0;
 	int ret;
 
 	memset(op_ctx, 0, sizeof(*op_ctx));
-	op_ctx->va.range = size;
-	op_ctx->va.addr = va;
+	op_ctx->va.range = op->size;
+	op_ctx->va.addr = op->va;
 	op_ctx->flags = DRM_PANTHOR_VM_BIND_OP_TYPE_UNMAP;
 
 	/* Pre-allocate L3 page tables to account for the split-2M-block
 	 * situation on unmap.
 	 */
-	if (va != ALIGN(va, SZ_2M))
+	if (op->va != ALIGN(op->va, SZ_2M))
 		pt_count++;
 
-	if (va + size != ALIGN(va + size, SZ_2M) &&
-	    ALIGN(va + size, SZ_2M) != ALIGN(va, SZ_2M))
+	if (op->va + op->size != ALIGN(op->va + op->size, SZ_2M) &&
+	    ALIGN(op->va + op->size, SZ_2M) != ALIGN(op->va, SZ_2M))
 		pt_count++;
 
 	ret = panthor_vm_op_ctx_prealloc_vmas(op_ctx);
@@ -3012,7 +3012,7 @@ panthor_vm_bind_prepare_op_ctx(struct drm_file *file,
 		if (op->bo_handle || op->bo_offset)
 			return -EINVAL;
 
-		return panthor_vm_prepare_unmap_op_ctx(op_ctx, vm, op->va, op->size);
+		return panthor_vm_prepare_unmap_op_ctx(op_ctx, vm, op);
 
 	case DRM_PANTHOR_VM_BIND_OP_TYPE_SYNC_ONLY:
 		if (op->flags & ~DRM_PANTHOR_VM_BIND_OP_TYPE_MASK)
@@ -3232,10 +3232,14 @@ int panthor_vm_map_bo_range(struct panthor_vm *vm, struct panthor_gem_object *bo
  */
 int panthor_vm_unmap_range(struct panthor_vm *vm, u64 va, u64 size)
 {
+	struct drm_panthor_vm_bind_op op = {
+		.size = size,
+		.va = va,
+	};
 	struct panthor_vm_op_ctx op_ctx;
 	int ret;
 
-	ret = panthor_vm_prepare_unmap_op_ctx(&op_ctx, vm, va, size);
+	ret = panthor_vm_prepare_unmap_op_ctx(&op_ctx, vm, &op);
 	if (ret)
 		return ret;
 

-- 
2.54.0

[PATCH v3 4/4] drm/panthor: Check for sparse binding range overflow

[Adrián Larumbe]

This check is being already carried out further down the call stack inside
drm_gpuvm_sm_map -> drm_gpuvm_range_valid, but it's best to fail early in
the driver before GPUVM functions are invoked so that we won't waste time
allocating vm_bind context resources.

Reported-by: Sashiko <noreply@sashiko.dev>
Closes: https://sashiko.dev/#/message/20260623204220.CDB1B1F000E9%40smtp.kernel.org
Fixes: 12cf826bf1dd ("drm/panthor: Support sparse mappings")
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 77fdad4e5166..8bd9b975e5ce 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -1328,6 +1328,7 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
 	struct drm_gpuvm_bo *preallocated_vm_bo;
 	struct sg_table *sgt = NULL;
 	int ret;
+	u64 end;
 
 	if (!bo)
 		return -EINVAL;
@@ -1353,6 +1354,10 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
 	if (is_sparse && (op->bo_handle || op->bo_offset))
 		return -EINVAL;
 
+	/* Protect against sparse VA range overflow */
+	if (is_sparse && check_add_overflow(op->va, op->size, &end))
+		return -EINVAL;
+
 	/* If the BO has an exclusive VM attached, it can't be mapped to other VMs. */
 	if (bo->exclusive_vm_root_gem &&
 	    bo->exclusive_vm_root_gem != panthor_vm_root_gem(vm))
@@ -1418,7 +1423,9 @@ static int panthor_vm_prepare_unmap_op_ctx(struct panthor_vm_op_ctx *op_ctx,
 					   struct panthor_vm *vm,
 					   const struct drm_panthor_vm_bind_op *op)
 {
+	bool is_sparse = op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE;
 	u32 pt_count = 0;
+	u64 end;
 	int ret;
 
 	memset(op_ctx, 0, sizeof(*op_ctx));
@@ -1432,6 +1439,10 @@ static int panthor_vm_prepare_unmap_op_ctx(struct panthor_vm_op_ctx *op_ctx,
 	if (op->va != ALIGN(op->va, SZ_2M))
 		pt_count++;
 
+	/* Protect against sparse VA range overflow */
+	if (is_sparse && check_add_overflow(op->va, op->size, &end))
+		return -EINVAL;
+
 	if (op->va + op->size != ALIGN(op->va + op->size, SZ_2M) &&
 	    ALIGN(op->va + op->size, SZ_2M) != ALIGN(op->va, SZ_2M))
 		pt_count++;

-- 
2.54.0

Re: [PATCH v3 4/4] drm/panthor: Check for sparse binding range overflow

[Boris Brezillon]

On Mon, 29 Jun 2026 21:17:08 +0100
Adrián Larumbe <adrian.larumbe@collabora.com> wrote:

> This check is being already carried out further down the call stack inside
> drm_gpuvm_sm_map -> drm_gpuvm_range_valid, but it's best to fail early in
> the driver before GPUVM functions are invoked so that we won't waste time
> allocating vm_bind context resources.
> 
> Reported-by: Sashiko <noreply@sashiko.dev>
> Closes: https://sashiko.dev/#/message/20260623204220.CDB1B1F000E9%40smtp.kernel.org
> Fixes: 12cf826bf1dd ("drm/panthor: Support sparse mappings")
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 77fdad4e5166..8bd9b975e5ce 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -1328,6 +1328,7 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  	struct drm_gpuvm_bo *preallocated_vm_bo;
>  	struct sg_table *sgt = NULL;
>  	int ret;
> +	u64 end;
>  
>  	if (!bo)
>  		return -EINVAL;
> @@ -1353,6 +1354,10 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  	if (is_sparse && (op->bo_handle || op->bo_offset))
>  		return -EINVAL;
>  
> +	/* Protect against sparse VA range overflow */
> +	if (is_sparse && check_add_overflow(op->va, op->size, &end))
> +		return -EINVAL;

Why should we limit this to sparse? Feels like the overflow check is
good to have for non-sparse as well.

> +
>  	/* If the BO has an exclusive VM attached, it can't be mapped to other VMs. */
>  	if (bo->exclusive_vm_root_gem &&
>  	    bo->exclusive_vm_root_gem != panthor_vm_root_gem(vm))
> @@ -1418,7 +1423,9 @@ static int panthor_vm_prepare_unmap_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  					   struct panthor_vm *vm,
>  					   const struct drm_panthor_vm_bind_op *op)
>  {
> +	bool is_sparse = op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE;
>  	u32 pt_count = 0;
> +	u64 end;
>  	int ret;
>  
>  	memset(op_ctx, 0, sizeof(*op_ctx));
> @@ -1432,6 +1439,10 @@ static int panthor_vm_prepare_unmap_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  	if (op->va != ALIGN(op->va, SZ_2M))
>  		pt_count++;
>  
> +	/* Protect against sparse VA range overflow */
> +	if (is_sparse && check_add_overflow(op->va, op->size, &end))
> +		return -EINVAL;
> +
>  	if (op->va + op->size != ALIGN(op->va + op->size, SZ_2M) &&
>  	    ALIGN(op->va + op->size, SZ_2M) != ALIGN(op->va, SZ_2M))
>  		pt_count++;
> 

Re: [PATCH v3 4/4] drm/panthor: Check for sparse binding range overflow

[Adrián Larumbe]

On 2026-06-30 10:23:36+02:00, Boris Brezillon wrote:
> On Mon, 29 Jun 2026 21:17:08 +0100
> Adrián Larumbe <adrian.larumbe@collabora.com> wrote:
> 
> > This check is being already carried out further down the call stack inside
> > drm_gpuvm_sm_map -> drm_gpuvm_range_valid, but it's best to fail early in
> > the driver before GPUVM functions are invoked so that we won't waste time
> > allocating vm_bind context resources.
> > 
> > Reported-by: Sashiko <noreply@sashiko.dev>
> > Closes: https://sashiko.dev/#/message/20260623204220.CDB1B1F000E9%40smtp.kernel.org
> > Fixes: 12cf826bf1dd ("drm/panthor: Support sparse mappings")
> > Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> > ---
> >  drivers/gpu/drm/panthor/panthor_mmu.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> > index 77fdad4e5166..8bd9b975e5ce 100644
> > --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> > @@ -1328,6 +1328,7 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
> >  	struct drm_gpuvm_bo *preallocated_vm_bo;
> >  	struct sg_table *sgt = NULL;
> >  	int ret;
> > +	u64 end;
> >  
> >  	if (!bo)
> >  		return -EINVAL;
> > @@ -1353,6 +1354,10 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
> >  	if (is_sparse && (op->bo_handle || op->bo_offset))
> >  		return -EINVAL;
> >  
> > +	/* Protect against sparse VA range overflow */
> > +	if (is_sparse && check_add_overflow(op->va, op->size, &end))
> > +		return -EINVAL;
> 
> Why should we limit this to sparse? Feels like the overflow check is
> good to have for non-sparse as well.

You're right, it should be done for all unmaps. On top of that, Sashiko pointed this out:

New issues:
- [Low] The newly added overflow check in `panthor_vm_prepare_unmap_op_ctx` is mathematically dead code because the `MAP_SPARSE` flag is explicitly rejected for UNMAP operations.
- [Low] The overflow check in `panthor_vm_prepare_map_op_ctx` is artificially restricted to sparse mappings, bypassing early protection for non-sparse mappings.

So it turns out that by limiting the overflow check to sparse unmaps, I've introduced a NOP.
That also made me think that even though in the uAPI we state the following:

* @DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE: Sparsely map a virtual memory range
*
* Only valid with DRM_PANTHOR_VM_BIND_OP_TYPE_MAP.

I wrote no checks to validate this for the sparse mappings patch series.
So for v4 I'll be doing the overflow check unconditionally in panthor_vm_prepare_unmap_op_ctx() and also
return -EINVAL if DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE is among the op flags.

Second Sashiko issue isn't relevant because right at the next statement we're clamping limiting mapping
ranges to the size of BOs.

Cheers,
Adrian

Re: [PATCH v3 1/4] drm/panthor: Add vm_bind region with kbo range overlap check

[Steven Price]

On 29/06/2026 21:17, Adrián Larumbe wrote:
> When a VM is created, caller has to specify the range of the address space
> carve-out set aside for mapping kernel BO's. That means vm_bind mappings of
> UM-exposed BO's should not intersect with that region, but at the moment
> we're not checking this.
> 
> At first, I thought of giving these values to drm_gpuvm_init() through its
> reserve_{offset, range} arguments, but it turns out that is meant for VM
> address spans that are not managed through the usual drm_gpuvm split/merge
> circuit, so storing the end of the user VA range at VM creation time and
> doing a quick check in the vm_bind ioctl path was the simplest workaround.
> 
> Fixes: tag and reference the relevant sparse binding support commit.
> Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 31cc57029c12..94789777aac4 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -310,6 +310,9 @@ struct panthor_vm {
>  		u64 end;
>  	} kernel_auto_va;
>  
> +	/** @user_va_range: Upper boundary of VAs VM users can map objects against. */
> +	u64 user_va_range;
> +
>  	/** @as: Address space related fields. */
>  	struct {
>  		/**
> @@ -2893,6 +2896,8 @@ panthor_vm_create(struct panthor_device *ptdev, bool for_mcu,
>  		va_range = full_va_range;
>  	}
>  
> +	vm->user_va_range = kernel_va_start;
> +
>  	mutex_init(&vm->mm_lock);
>  	drm_mm_init(&vm->mm, kernel_va_start, kernel_va_size);
>  	vm->kernel_auto_va.start = auto_kernel_va_start;
> @@ -2981,6 +2986,10 @@ panthor_vm_bind_prepare_op_ctx(struct drm_file *file,
>  	if (!IS_ALIGNED(op->va | op->size | op->bo_offset, vm_pgsz))
>  		return -EINVAL;
>  
> +	/* We don't allow mappings that overlap with kbo's reserved range */
> +	if (op->va + op->size > vm->user_va_range)

This can overflow, although you partially handle this case in patch 4.
Can we simply move the overflow check from patch 4 here along with the
user_va_range check?

Thanks,
Steve

> +		return -EINVAL;
> +
>  	switch (op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) {
>  	case DRM_PANTHOR_VM_BIND_OP_TYPE_MAP:
>  		if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) {
>