[PATCH v3 0/3] xen/privcmd: support for dm_op and restriction

[PATCH v3 0/3] xen/privcmd: support for dm_op and restriction

[Paul Durrant]

This patch series follows on from my recent Xen series [1], to provide
support in privcmd for de-privileging of device emulators.

[1] https://lists.xen.org/archives/html/xen-devel/2017-01/msg02558.html

Paul Durrant (3):
  xen/privcmd: return -ENOTTY for unimplemented IOCTLs
  xen/privcmd: Add IOCTL_PRIVCMD_DM_OP
  xen/privcmd: add IOCTL_PRIVCMD_RESTRICT

 arch/arm/xen/enlighten.c             |   1 +
 arch/arm/xen/hypercall.S             |   1 +
 arch/arm64/xen/hypercall.S           |   1 +
 arch/x86/include/asm/xen/hypercall.h |   7 ++
 drivers/xen/privcmd.c                | 226 +++++++++++++++++++++++++++++++++--
 include/uapi/xen/privcmd.h           |  15 +++
 include/xen/arm/hypercall.h          |   1 +
 include/xen/interface/hvm/dm_op.h    |  32 +++++
 include/xen/interface/xen.h          |   1 +
 9 files changed, 276 insertions(+), 9 deletions(-)
 create mode 100644 include/xen/interface/hvm/dm_op.h

-- 
2.1.4

[PATCH v3 1/3] xen/privcmd: return -ENOTTY for unimplemented IOCTLs

[Paul Durrant]

The code sets the default return code to -ENOSYS but then overrides this
to -EINVAL in the switch() statement's default case, which is clearly
silly.

This patch removes the override and sets the default return code to
-ENOTTY, which is the conventional return for an unimplemented ioctl.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
---
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>

v2:
- Use -ENOTTY rather than -ENOSYS
---
 drivers/xen/privcmd.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 6e3306f..5e5c7ae 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -551,7 +551,7 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
 static long privcmd_ioctl(struct file *file,
 			  unsigned int cmd, unsigned long data)
 {
-	int ret = -ENOSYS;
+	int ret = -ENOTTY;
 	void __user *udata = (void __user *) data;
 
 	switch (cmd) {
@@ -572,7 +572,6 @@ static long privcmd_ioctl(struct file *file,
 		break;
 
 	default:
-		ret = -EINVAL;
 		break;
 	}
 
-- 
2.1.4

Re: [PATCH v3 1/3] xen/privcmd: return -ENOTTY for unimplemented IOCTLs

[Boris Ostrovsky]

On 02/13/2017 12:03 PM, Paul Durrant wrote:
> The code sets the default return code to -ENOSYS but then overrides this
> to -EINVAL in the switch() statement's default case, which is clearly
> silly.
>
> This patch removes the override and sets the default return code to
> -ENOTTY, which is the conventional return for an unimplemented ioctl.
>
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>

Applied to for-linus-4.11.

-boris

[PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

[Paul Durrant]

Recently a new dm_op[1] hypercall was added to Xen to provide a mechanism
for restricting device emulators (such as QEMU) to a limited set of
hypervisor operations, and being able to audit those operations in the
kernel of the domain in which they run.

This patch adds IOCTL_PRIVCMD_DM_OP as gateway for __HYPERVISOR_dm_op.

NOTE: There is no requirement for user-space code to bounce data through
      locked memory buffers (as with IOCTL_PRIVCMD_HYPERCALL) since
      privcmd has enough information to lock the original buffers
      directly.

[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=524a98c2

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
---
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>

v3:
- Add module parameters for max number of dm_op buffers and max buffer
  size
- Fix arm build
- Fix commit comment to reflect re-worked patch

v2:
- Lock the user pages rather than bouncing through kernel memory
---
 arch/arm/xen/enlighten.c             |   1 +
 arch/arm/xen/hypercall.S             |   1 +
 arch/arm64/xen/hypercall.S           |   1 +
 arch/x86/include/asm/xen/hypercall.h |   7 ++
 drivers/xen/privcmd.c                | 139 +++++++++++++++++++++++++++++++++++
 include/uapi/xen/privcmd.h           |  13 ++++
 include/xen/arm/hypercall.h          |   1 +
 include/xen/interface/hvm/dm_op.h    |  32 ++++++++
 include/xen/interface/xen.h          |   1 +
 9 files changed, 196 insertions(+)
 create mode 100644 include/xen/interface/hvm/dm_op.h

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 11d9f28..81e3217 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -457,4 +457,5 @@ EXPORT_SYMBOL_GPL(HYPERVISOR_tmem_op);
 EXPORT_SYMBOL_GPL(HYPERVISOR_platform_op);
 EXPORT_SYMBOL_GPL(HYPERVISOR_multicall);
 EXPORT_SYMBOL_GPL(HYPERVISOR_vm_assist);
+EXPORT_SYMBOL_GPL(HYPERVISOR_dm_op);
 EXPORT_SYMBOL_GPL(privcmd_call);
diff --git a/arch/arm/xen/hypercall.S b/arch/arm/xen/hypercall.S
index a648dfc..b0b80c0 100644
--- a/arch/arm/xen/hypercall.S
+++ b/arch/arm/xen/hypercall.S
@@ -92,6 +92,7 @@ HYPERCALL1(tmem_op);
 HYPERCALL1(platform_op_raw);
 HYPERCALL2(multicall);
 HYPERCALL2(vm_assist);
+HYPERCALL3(dm_op);
 
 ENTRY(privcmd_call)
 	stmdb sp!, {r4}
diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S
index 947830a..401ceb7 100644
--- a/arch/arm64/xen/hypercall.S
+++ b/arch/arm64/xen/hypercall.S
@@ -84,6 +84,7 @@ HYPERCALL1(tmem_op);
 HYPERCALL1(platform_op_raw);
 HYPERCALL2(multicall);
 HYPERCALL2(vm_assist);
+HYPERCALL3(dm_op);
 
 ENTRY(privcmd_call)
 	mov x16, x0
diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
index a12a047..f6d20f6 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -472,6 +472,13 @@ HYPERVISOR_xenpmu_op(unsigned int op, void *arg)
 	return _hypercall2(int, xenpmu_op, op, arg);
 }
 
+static inline int
+HYPERVISOR_dm_op(
+	domid_t dom, unsigned int nr_bufs, void *bufs)
+{
+	return _hypercall3(int, dm_op, dom, nr_bufs, bufs);
+}
+
 static inline void
 MULTI_fpu_taskswitch(struct multicall_entry *mcl, int set)
 {
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 5e5c7ae..a33f17e 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -22,6 +22,7 @@
 #include <linux/pagemap.h>
 #include <linux/seq_file.h>
 #include <linux/miscdevice.h>
+#include <linux/moduleparam.h>
 
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
@@ -32,6 +33,7 @@
 #include <xen/xen.h>
 #include <xen/privcmd.h>
 #include <xen/interface/xen.h>
+#include <xen/interface/hvm/dm_op.h>
 #include <xen/features.h>
 #include <xen/page.h>
 #include <xen/xen-ops.h>
@@ -43,6 +45,17 @@ MODULE_LICENSE("GPL");
 
 #define PRIV_VMA_LOCKED ((void *)1)
 
+unsigned int privcmd_dm_op_max_num = 16;
+module_param_named(dm_op_max_nr_bufs, privcmd_dm_op_max_num, uint, 0644);
+MODULE_PARM_DESC(dm_op_max_nr_bufs,
+		 "Maximum number of buffers per dm_op hypercall");
+
+unsigned int privcmd_dm_op_buf_max_size = XEN_PAGE_SIZE;
+module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint,
+		   0644);
+MODULE_PARM_DESC(dm_op_buf_max_size,
+		 "Maximum size of a dm_op hypercall buffer");
+
 static int privcmd_vma_range_is_mapped(
                struct vm_area_struct *vma,
                unsigned long addr,
@@ -548,6 +561,128 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
 	goto out;
 }
 
+static int lock_pages(
+	struct privcmd_dm_op_buf kbufs[], unsigned int num,
+	struct page *pages[], unsigned int nr_pages)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++) {
+		unsigned int requested;
+		int pinned;
+
+		requested = DIV_ROUND_UP(
+			offset_in_page(kbufs[i].uptr) + kbufs[i].size,
+			PAGE_SIZE);
+		if (requested > nr_pages)
+			return -ENOSPC;
+
+		pinned = get_user_pages_fast(
+			(unsigned long) kbufs[i].uptr,
+			requested, FOLL_WRITE, pages);
+		if (pinned < 0)
+			return pinned;
+
+		nr_pages -= pinned;
+		pages += pinned;
+	}
+
+	return 0;
+}
+
+static void unlock_pages(struct page *pages[], unsigned int nr_pages)
+{
+	unsigned int i;
+
+	if (!pages)
+		return;
+
+	for (i = 0; i < nr_pages; i++) {
+		if (pages[i])
+			put_page(pages[i]);
+	}
+}
+
+static long privcmd_ioctl_dm_op(void __user *udata)
+{
+	struct privcmd_dm_op kdata;
+	struct privcmd_dm_op_buf *kbufs;
+	unsigned int nr_pages = 0;
+	struct page **pages = NULL;
+	struct xen_dm_op_buf *xbufs = NULL;
+	unsigned int i;
+	long rc;
+
+	if (copy_from_user(&kdata, udata, sizeof(kdata)))
+		return -EFAULT;
+
+	if (kdata.num == 0)
+		return 0;
+
+	if (kdata.num > privcmd_dm_op_max_num)
+		return -E2BIG;
+
+	kbufs = kcalloc(kdata.num, sizeof(*kbufs), GFP_KERNEL);
+	if (!kbufs)
+		return -ENOMEM;
+
+	if (copy_from_user(kbufs, kdata.ubufs,
+			   sizeof(*kbufs) * kdata.num)) {
+		rc = -EFAULT;
+		goto out;
+	}
+
+	for (i = 0; i < kdata.num; i++) {
+		if (kbufs[i].size > privcmd_dm_op_buf_max_size) {
+			rc = -E2BIG;
+			goto out;
+		}
+
+		if (!access_ok(VERIFY_WRITE, kbufs[i].uptr,
+			       kbufs[i].size)) {
+			rc = -EFAULT;
+			goto out;
+		}
+
+		nr_pages += DIV_ROUND_UP(
+			offset_in_page(kbufs[i].uptr) + kbufs[i].size,
+			PAGE_SIZE);
+	}
+
+	pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
+	if (!pages) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	xbufs = kcalloc(kdata.num, sizeof(*xbufs), GFP_KERNEL);
+	if (!xbufs) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	rc = lock_pages(kbufs, kdata.num, pages, nr_pages);
+	if (rc)
+		goto out;
+
+	for (i = 0; i < kdata.num; i++) {
+		set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr);
+		xbufs[i].size = kbufs[i].size;
+	}
+
+	xen_preemptible_hcall_begin();
+	rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
+	xen_preemptible_hcall_end();
+
+out:
+	unlock_pages(pages, nr_pages);
+	kfree(xbufs);
+	kfree(pages);
+	kfree(kbufs);
+
+	return rc;
+}
+
 static long privcmd_ioctl(struct file *file,
 			  unsigned int cmd, unsigned long data)
 {
@@ -571,6 +706,10 @@ static long privcmd_ioctl(struct file *file,
 		ret = privcmd_ioctl_mmap_batch(udata, 2);
 		break;
 
+	case IOCTL_PRIVCMD_DM_OP:
+		ret = privcmd_ioctl_dm_op(udata);
+		break;
+
 	default:
 		break;
 	}
diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h
index 7ddeeda..f8c5d75 100644
--- a/include/uapi/xen/privcmd.h
+++ b/include/uapi/xen/privcmd.h
@@ -77,6 +77,17 @@ struct privcmd_mmapbatch_v2 {
 	int __user *err;  /* array of error codes */
 };
 
+struct privcmd_dm_op_buf {
+	void __user *uptr;
+	size_t size;
+};
+
+struct privcmd_dm_op {
+	domid_t dom;
+	__u16 num;
+	const struct privcmd_dm_op_buf __user *ubufs;
+};
+
 /*
  * @cmd: IOCTL_PRIVCMD_HYPERCALL
  * @arg: &privcmd_hypercall_t
@@ -98,5 +109,7 @@ struct privcmd_mmapbatch_v2 {
 	_IOC(_IOC_NONE, 'P', 3, sizeof(struct privcmd_mmapbatch))
 #define IOCTL_PRIVCMD_MMAPBATCH_V2				\
 	_IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2))
+#define IOCTL_PRIVCMD_DM_OP					\
+	_IOC(_IOC_NONE, 'P', 5, sizeof(struct privcmd_dm_op))
 
 #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
diff --git a/include/xen/arm/hypercall.h b/include/xen/arm/hypercall.h
index 9d874db..73db4b2 100644
--- a/include/xen/arm/hypercall.h
+++ b/include/xen/arm/hypercall.h
@@ -53,6 +53,7 @@ int HYPERVISOR_physdev_op(int cmd, void *arg);
 int HYPERVISOR_vcpu_op(int cmd, int vcpuid, void *extra_args);
 int HYPERVISOR_tmem_op(void *arg);
 int HYPERVISOR_vm_assist(unsigned int cmd, unsigned int type);
+int HYPERVISOR_dm_op(domid_t domid, unsigned int nr_bufs, void *bufs);
 int HYPERVISOR_platform_op_raw(void *arg);
 static inline int HYPERVISOR_platform_op(struct xen_platform_op *op)
 {
diff --git a/include/xen/interface/hvm/dm_op.h b/include/xen/interface/hvm/dm_op.h
new file mode 100644
index 0000000..ee9e480
--- /dev/null
+++ b/include/xen/interface/hvm/dm_op.h
@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2016, Citrix Systems Inc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef __XEN_PUBLIC_HVM_DM_OP_H__
+#define __XEN_PUBLIC_HVM_DM_OP_H__
+
+struct xen_dm_op_buf {
+	GUEST_HANDLE(void) h;
+	xen_ulong_t size;
+};
+DEFINE_GUEST_HANDLE_STRUCT(xen_dm_op_buf);
+
+#endif /* __XEN_PUBLIC_HVM_DM_OP_H__ */
diff --git a/include/xen/interface/xen.h b/include/xen/interface/xen.h
index 1b0d189..4f4830e 100644
--- a/include/xen/interface/xen.h
+++ b/include/xen/interface/xen.h
@@ -81,6 +81,7 @@
 #define __HYPERVISOR_tmem_op              38
 #define __HYPERVISOR_xc_reserved_op       39 /* reserved for XenClient */
 #define __HYPERVISOR_xenpmu_op            40
+#define __HYPERVISOR_dm_op                41
 
 /* Architecture-specific hypercall definitions. */
 #define __HYPERVISOR_arch_0               48
-- 
2.1.4

Re: [PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

[Boris Ostrovsky]

> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index 5e5c7ae..a33f17e 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -22,6 +22,7 @@
>  #include <linux/pagemap.h>
>  #include <linux/seq_file.h>
>  #include <linux/miscdevice.h>
> +#include <linux/moduleparam.h>
>
>  #include <asm/pgalloc.h>
>  #include <asm/pgtable.h>
> @@ -32,6 +33,7 @@
>  #include <xen/xen.h>
>  #include <xen/privcmd.h>
>  #include <xen/interface/xen.h>
> +#include <xen/interface/hvm/dm_op.h>
>  #include <xen/features.h>
>  #include <xen/page.h>
>  #include <xen/xen-ops.h>
> @@ -43,6 +45,17 @@ MODULE_LICENSE("GPL");
>
>  #define PRIV_VMA_LOCKED ((void *)1)
>
> +unsigned int privcmd_dm_op_max_num = 16;
> +module_param_named(dm_op_max_nr_bufs, privcmd_dm_op_max_num, uint, 0644);
> +MODULE_PARM_DESC(dm_op_max_nr_bufs,
> +		 "Maximum number of buffers per dm_op hypercall");
> +
> +unsigned int privcmd_dm_op_buf_max_size = XEN_PAGE_SIZE;

These need to be static. (I can fix it when committing.)

And I am still not sure about using XEN_PAGE_SIZE. There is no 
dependency in the hypervisor on buffers being page-sized, is there? If 
not, XEN_PAGE_SIZE is here just because it happens to be 4K, which is a 
reasonable value.

How about just setting it to 4096?


-boris

RE: [PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

[Paul Durrant]

My previous reply got bounced because my tablet insisted on using HTML...

> -----Original Message-----
> 
> These need to be static. (I can fix it when committing.)

Ok, thanks.

> 
> And I am still not sure about using XEN_PAGE_SIZE. There is no
> dependency in the hypervisor on buffers being page-sized, is there? If
> not, XEN_PAGE_SIZE is here just because it happens to be 4K, which is a
> reasonable value.
> 
> How about just setting it to 4096?
> 

I chose XEN_PAGE_SIZE because the hypercall will eventually copy in the buffer so it seemed like a reasonable value to use. If you want to just use 4096 then I am ok with that.

  Paul

PS: If you want to change from XEN_PAGE_SIZE to 4096 then I assume you are happy to do this at commit and don't need me to send a v4?

> 
> -boris

Re: [PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

[Boris Ostrovsky]

On 02/14/2017 04:20 AM, Paul Durrant wrote:
> My previous reply got bounced because my tablet insisted on using HTML...
>
>> -----Original Message-----
>>
>> These need to be static. (I can fix it when committing.)
>
> Ok, thanks.
>
>>
>> And I am still not sure about using XEN_PAGE_SIZE. There is no
>> dependency in the hypervisor on buffers being page-sized, is there? If
>> not, XEN_PAGE_SIZE is here just because it happens to be 4K, which is a
>> reasonable value.
>>
>> How about just setting it to 4096?
>>
>
> I chose XEN_PAGE_SIZE because the hypercall will eventually copy in the buffer so it seemed like a reasonable value to use. If you want to just use 4096 then I am ok with that.
>
>   Paul
>
> PS: If you want to change from XEN_PAGE_SIZE to 4096 then I assume you are happy to do this at commit and don't need me to send a v4?

Right.

But I also had a question about patch 3 (commit message). I can make the 
change when committing as well but I need to make sure you are OK with it.

-boris

Re: [PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

[Boris Ostrovsky]

On 02/13/2017 12:03 PM, Paul Durrant wrote:
> Recently a new dm_op[1] hypercall was added to Xen to provide a mechanism
> for restricting device emulators (such as QEMU) to a limited set of
> hypervisor operations, and being able to audit those operations in the
> kernel of the domain in which they run.
>
> This patch adds IOCTL_PRIVCMD_DM_OP as gateway for __HYPERVISOR_dm_op.
>
> NOTE: There is no requirement for user-space code to bounce data through
>       locked memory buffers (as with IOCTL_PRIVCMD_HYPERCALL) since
>       privcmd has enough information to lock the original buffers
>       directly.
>
> [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=524a98c2
>
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>


Stefano,

Are you OK with ARM changes?

-boris



> ---
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: Juergen Gross <jgross@suse.com>
>
> v3:
> - Add module parameters for max number of dm_op buffers and max buffer
>   size
> - Fix arm build
> - Fix commit comment to reflect re-worked patch
>
> v2:
> - Lock the user pages rather than bouncing through kernel memory
> ---
>  arch/arm/xen/enlighten.c             |   1 +
>  arch/arm/xen/hypercall.S             |   1 +
>  arch/arm64/xen/hypercall.S           |   1 +
>  arch/x86/include/asm/xen/hypercall.h |   7 ++
>  drivers/xen/privcmd.c                | 139 +++++++++++++++++++++++++++++++++++
>  include/uapi/xen/privcmd.h           |  13 ++++
>  include/xen/arm/hypercall.h          |   1 +
>  include/xen/interface/hvm/dm_op.h    |  32 ++++++++
>  include/xen/interface/xen.h          |   1 +
>  9 files changed, 196 insertions(+)
>  create mode 100644 include/xen/interface/hvm/dm_op.h
>
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 11d9f28..81e3217 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -457,4 +457,5 @@ EXPORT_SYMBOL_GPL(HYPERVISOR_tmem_op);
>  EXPORT_SYMBOL_GPL(HYPERVISOR_platform_op);
>  EXPORT_SYMBOL_GPL(HYPERVISOR_multicall);
>  EXPORT_SYMBOL_GPL(HYPERVISOR_vm_assist);
> +EXPORT_SYMBOL_GPL(HYPERVISOR_dm_op);
>  EXPORT_SYMBOL_GPL(privcmd_call);
> diff --git a/arch/arm/xen/hypercall.S b/arch/arm/xen/hypercall.S
> index a648dfc..b0b80c0 100644
> --- a/arch/arm/xen/hypercall.S
> +++ b/arch/arm/xen/hypercall.S
> @@ -92,6 +92,7 @@ HYPERCALL1(tmem_op);
>  HYPERCALL1(platform_op_raw);
>  HYPERCALL2(multicall);
>  HYPERCALL2(vm_assist);
> +HYPERCALL3(dm_op);
>  
>  ENTRY(privcmd_call)
>  	stmdb sp!, {r4}
> diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S
> index 947830a..401ceb7 100644
> --- a/arch/arm64/xen/hypercall.S
> +++ b/arch/arm64/xen/hypercall.S
> @@ -84,6 +84,7 @@ HYPERCALL1(tmem_op);
>  HYPERCALL1(platform_op_raw);
>  HYPERCALL2(multicall);
>  HYPERCALL2(vm_assist);
> +HYPERCALL3(dm_op);
>  
>  ENTRY(privcmd_call)
>  	mov x16, x0
> diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
> index a12a047..f6d20f6 100644
> --- a/arch/x86/include/asm/xen/hypercall.h
> +++ b/arch/x86/include/asm/xen/hypercall.h
> @@ -472,6 +472,13 @@ HYPERVISOR_xenpmu_op(unsigned int op, void *arg)
>  	return _hypercall2(int, xenpmu_op, op, arg);
>  }
>  
> +static inline int
> +HYPERVISOR_dm_op(
> +	domid_t dom, unsigned int nr_bufs, void *bufs)
> +{
> +	return _hypercall3(int, dm_op, dom, nr_bufs, bufs);
> +}
> +
>  static inline void
>  MULTI_fpu_taskswitch(struct multicall_entry *mcl, int set)
>  {
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index 5e5c7ae..a33f17e 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -22,6 +22,7 @@
>  #include <linux/pagemap.h>
>  #include <linux/seq_file.h>
>  #include <linux/miscdevice.h>
> +#include <linux/moduleparam.h>
>  
>  #include <asm/pgalloc.h>
>  #include <asm/pgtable.h>
> @@ -32,6 +33,7 @@
>  #include <xen/xen.h>
>  #include <xen/privcmd.h>
>  #include <xen/interface/xen.h>
> +#include <xen/interface/hvm/dm_op.h>
>  #include <xen/features.h>
>  #include <xen/page.h>
>  #include <xen/xen-ops.h>
> @@ -43,6 +45,17 @@ MODULE_LICENSE("GPL");
>  
>  #define PRIV_VMA_LOCKED ((void *)1)
>  
> +unsigned int privcmd_dm_op_max_num = 16;
> +module_param_named(dm_op_max_nr_bufs, privcmd_dm_op_max_num, uint, 0644);
> +MODULE_PARM_DESC(dm_op_max_nr_bufs,
> +		 "Maximum number of buffers per dm_op hypercall");
> +
> +unsigned int privcmd_dm_op_buf_max_size = XEN_PAGE_SIZE;
> +module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint,
> +		   0644);
> +MODULE_PARM_DESC(dm_op_buf_max_size,
> +		 "Maximum size of a dm_op hypercall buffer");
> +
>  static int privcmd_vma_range_is_mapped(
>                 struct vm_area_struct *vma,
>                 unsigned long addr,
> @@ -548,6 +561,128 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
>  	goto out;
>  }
>  
> +static int lock_pages(
> +	struct privcmd_dm_op_buf kbufs[], unsigned int num,
> +	struct page *pages[], unsigned int nr_pages)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < num; i++) {
> +		unsigned int requested;
> +		int pinned;
> +
> +		requested = DIV_ROUND_UP(
> +			offset_in_page(kbufs[i].uptr) + kbufs[i].size,
> +			PAGE_SIZE);
> +		if (requested > nr_pages)
> +			return -ENOSPC;
> +
> +		pinned = get_user_pages_fast(
> +			(unsigned long) kbufs[i].uptr,
> +			requested, FOLL_WRITE, pages);
> +		if (pinned < 0)
> +			return pinned;
> +
> +		nr_pages -= pinned;
> +		pages += pinned;
> +	}
> +
> +	return 0;
> +}
> +
> +static void unlock_pages(struct page *pages[], unsigned int nr_pages)
> +{
> +	unsigned int i;
> +
> +	if (!pages)
> +		return;
> +
> +	for (i = 0; i < nr_pages; i++) {
> +		if (pages[i])
> +			put_page(pages[i]);
> +	}
> +}
> +
> +static long privcmd_ioctl_dm_op(void __user *udata)
> +{
> +	struct privcmd_dm_op kdata;
> +	struct privcmd_dm_op_buf *kbufs;
> +	unsigned int nr_pages = 0;
> +	struct page **pages = NULL;
> +	struct xen_dm_op_buf *xbufs = NULL;
> +	unsigned int i;
> +	long rc;
> +
> +	if (copy_from_user(&kdata, udata, sizeof(kdata)))
> +		return -EFAULT;
> +
> +	if (kdata.num == 0)
> +		return 0;
> +
> +	if (kdata.num > privcmd_dm_op_max_num)
> +		return -E2BIG;
> +
> +	kbufs = kcalloc(kdata.num, sizeof(*kbufs), GFP_KERNEL);
> +	if (!kbufs)
> +		return -ENOMEM;
> +
> +	if (copy_from_user(kbufs, kdata.ubufs,
> +			   sizeof(*kbufs) * kdata.num)) {
> +		rc = -EFAULT;
> +		goto out;
> +	}
> +
> +	for (i = 0; i < kdata.num; i++) {
> +		if (kbufs[i].size > privcmd_dm_op_buf_max_size) {
> +			rc = -E2BIG;
> +			goto out;
> +		}
> +
> +		if (!access_ok(VERIFY_WRITE, kbufs[i].uptr,
> +			       kbufs[i].size)) {
> +			rc = -EFAULT;
> +			goto out;
> +		}
> +
> +		nr_pages += DIV_ROUND_UP(
> +			offset_in_page(kbufs[i].uptr) + kbufs[i].size,
> +			PAGE_SIZE);
> +	}
> +
> +	pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
> +	if (!pages) {
> +		rc = -ENOMEM;
> +		goto out;
> +	}
> +
> +	xbufs = kcalloc(kdata.num, sizeof(*xbufs), GFP_KERNEL);
> +	if (!xbufs) {
> +		rc = -ENOMEM;
> +		goto out;
> +	}
> +
> +	rc = lock_pages(kbufs, kdata.num, pages, nr_pages);
> +	if (rc)
> +		goto out;
> +
> +	for (i = 0; i < kdata.num; i++) {
> +		set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr);
> +		xbufs[i].size = kbufs[i].size;
> +	}
> +
> +	xen_preemptible_hcall_begin();
> +	rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
> +	xen_preemptible_hcall_end();
> +
> +out:
> +	unlock_pages(pages, nr_pages);
> +	kfree(xbufs);
> +	kfree(pages);
> +	kfree(kbufs);
> +
> +	return rc;
> +}
> +
>  static long privcmd_ioctl(struct file *file,
>  			  unsigned int cmd, unsigned long data)
>  {
> @@ -571,6 +706,10 @@ static long privcmd_ioctl(struct file *file,
>  		ret = privcmd_ioctl_mmap_batch(udata, 2);
>  		break;
>  
> +	case IOCTL_PRIVCMD_DM_OP:
> +		ret = privcmd_ioctl_dm_op(udata);
> +		break;
> +
>  	default:
>  		break;
>  	}
> diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h
> index 7ddeeda..f8c5d75 100644
> --- a/include/uapi/xen/privcmd.h
> +++ b/include/uapi/xen/privcmd.h
> @@ -77,6 +77,17 @@ struct privcmd_mmapbatch_v2 {
>  	int __user *err;  /* array of error codes */
>  };
>  
> +struct privcmd_dm_op_buf {
> +	void __user *uptr;
> +	size_t size;
> +};
> +
> +struct privcmd_dm_op {
> +	domid_t dom;
> +	__u16 num;
> +	const struct privcmd_dm_op_buf __user *ubufs;
> +};
> +
>  /*
>   * @cmd: IOCTL_PRIVCMD_HYPERCALL
>   * @arg: &privcmd_hypercall_t
> @@ -98,5 +109,7 @@ struct privcmd_mmapbatch_v2 {
>  	_IOC(_IOC_NONE, 'P', 3, sizeof(struct privcmd_mmapbatch))
>  #define IOCTL_PRIVCMD_MMAPBATCH_V2				\
>  	_IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2))
> +#define IOCTL_PRIVCMD_DM_OP					\
> +	_IOC(_IOC_NONE, 'P', 5, sizeof(struct privcmd_dm_op))
>  
>  #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
> diff --git a/include/xen/arm/hypercall.h b/include/xen/arm/hypercall.h
> index 9d874db..73db4b2 100644
> --- a/include/xen/arm/hypercall.h
> +++ b/include/xen/arm/hypercall.h
> @@ -53,6 +53,7 @@ int HYPERVISOR_physdev_op(int cmd, void *arg);
>  int HYPERVISOR_vcpu_op(int cmd, int vcpuid, void *extra_args);
>  int HYPERVISOR_tmem_op(void *arg);
>  int HYPERVISOR_vm_assist(unsigned int cmd, unsigned int type);
> +int HYPERVISOR_dm_op(domid_t domid, unsigned int nr_bufs, void *bufs);
>  int HYPERVISOR_platform_op_raw(void *arg);
>  static inline int HYPERVISOR_platform_op(struct xen_platform_op *op)
>  {
> diff --git a/include/xen/interface/hvm/dm_op.h b/include/xen/interface/hvm/dm_op.h
> new file mode 100644
> index 0000000..ee9e480
> --- /dev/null
> +++ b/include/xen/interface/hvm/dm_op.h
> @@ -0,0 +1,32 @@
> +/*
> + * Copyright (c) 2016, Citrix Systems Inc
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to
> + * deal in the Software without restriction, including without limitation the
> + * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
> + * sell copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
> + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + * DEALINGS IN THE SOFTWARE.
> + */
> +
> +#ifndef __XEN_PUBLIC_HVM_DM_OP_H__
> +#define __XEN_PUBLIC_HVM_DM_OP_H__
> +
> +struct xen_dm_op_buf {
> +	GUEST_HANDLE(void) h;
> +	xen_ulong_t size;
> +};
> +DEFINE_GUEST_HANDLE_STRUCT(xen_dm_op_buf);
> +
> +#endif /* __XEN_PUBLIC_HVM_DM_OP_H__ */
> diff --git a/include/xen/interface/xen.h b/include/xen/interface/xen.h
> index 1b0d189..4f4830e 100644
> --- a/include/xen/interface/xen.h
> +++ b/include/xen/interface/xen.h
> @@ -81,6 +81,7 @@
>  #define __HYPERVISOR_tmem_op              38
>  #define __HYPERVISOR_xc_reserved_op       39 /* reserved for XenClient */
>  #define __HYPERVISOR_xenpmu_op            40
> +#define __HYPERVISOR_dm_op                41
>  
>  /* Architecture-specific hypercall definitions. */
>  #define __HYPERVISOR_arch_0               48

Re: [PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

[Stefano Stabellini]

On Tue, 14 Feb 2017, Boris Ostrovsky wrote:
> On 02/13/2017 12:03 PM, Paul Durrant wrote:
> > Recently a new dm_op[1] hypercall was added to Xen to provide a mechanism
> > for restricting device emulators (such as QEMU) to a limited set of
> > hypervisor operations, and being able to audit those operations in the
> > kernel of the domain in which they run.
> >
> > This patch adds IOCTL_PRIVCMD_DM_OP as gateway for __HYPERVISOR_dm_op.
> >
> > NOTE: There is no requirement for user-space code to bounce data through
> >       locked memory buffers (as with IOCTL_PRIVCMD_HYPERCALL) since
> >       privcmd has enough information to lock the original buffers
> >       directly.
> >
> > [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=524a98c2
> >
> > Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> 
> 
> Stefano,
> 
> Are you OK with ARM changes?

Yes:

Acked-by: Stefano Stabellini <sstabellini@kernel.org>

Thanks for CC'ing me, I missed the patch.



> 
> 
> > ---
> > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> > Cc: Juergen Gross <jgross@suse.com>
> >
> > v3:
> > - Add module parameters for max number of dm_op buffers and max buffer
> >   size
> > - Fix arm build
> > - Fix commit comment to reflect re-worked patch
> >
> > v2:
> > - Lock the user pages rather than bouncing through kernel memory
> > ---
> >  arch/arm/xen/enlighten.c             |   1 +
> >  arch/arm/xen/hypercall.S             |   1 +
> >  arch/arm64/xen/hypercall.S           |   1 +
> >  arch/x86/include/asm/xen/hypercall.h |   7 ++
> >  drivers/xen/privcmd.c                | 139 +++++++++++++++++++++++++++++++++++
> >  include/uapi/xen/privcmd.h           |  13 ++++
> >  include/xen/arm/hypercall.h          |   1 +
> >  include/xen/interface/hvm/dm_op.h    |  32 ++++++++
> >  include/xen/interface/xen.h          |   1 +
> >  9 files changed, 196 insertions(+)
> >  create mode 100644 include/xen/interface/hvm/dm_op.h
> >
> > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > index 11d9f28..81e3217 100644
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -457,4 +457,5 @@ EXPORT_SYMBOL_GPL(HYPERVISOR_tmem_op);
> >  EXPORT_SYMBOL_GPL(HYPERVISOR_platform_op);
> >  EXPORT_SYMBOL_GPL(HYPERVISOR_multicall);
> >  EXPORT_SYMBOL_GPL(HYPERVISOR_vm_assist);
> > +EXPORT_SYMBOL_GPL(HYPERVISOR_dm_op);
> >  EXPORT_SYMBOL_GPL(privcmd_call);
> > diff --git a/arch/arm/xen/hypercall.S b/arch/arm/xen/hypercall.S
> > index a648dfc..b0b80c0 100644
> > --- a/arch/arm/xen/hypercall.S
> > +++ b/arch/arm/xen/hypercall.S
> > @@ -92,6 +92,7 @@ HYPERCALL1(tmem_op);
> >  HYPERCALL1(platform_op_raw);
> >  HYPERCALL2(multicall);
> >  HYPERCALL2(vm_assist);
> > +HYPERCALL3(dm_op);
> >  
> >  ENTRY(privcmd_call)
> >  	stmdb sp!, {r4}
> > diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S
> > index 947830a..401ceb7 100644
> > --- a/arch/arm64/xen/hypercall.S
> > +++ b/arch/arm64/xen/hypercall.S
> > @@ -84,6 +84,7 @@ HYPERCALL1(tmem_op);
> >  HYPERCALL1(platform_op_raw);
> >  HYPERCALL2(multicall);
> >  HYPERCALL2(vm_assist);
> > +HYPERCALL3(dm_op);
> >  
> >  ENTRY(privcmd_call)
> >  	mov x16, x0
> > diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
> > index a12a047..f6d20f6 100644
> > --- a/arch/x86/include/asm/xen/hypercall.h
> > +++ b/arch/x86/include/asm/xen/hypercall.h
> > @@ -472,6 +472,13 @@ HYPERVISOR_xenpmu_op(unsigned int op, void *arg)
> >  	return _hypercall2(int, xenpmu_op, op, arg);
> >  }
> >  
> > +static inline int
> > +HYPERVISOR_dm_op(
> > +	domid_t dom, unsigned int nr_bufs, void *bufs)
> > +{
> > +	return _hypercall3(int, dm_op, dom, nr_bufs, bufs);
> > +}
> > +
> >  static inline void
> >  MULTI_fpu_taskswitch(struct multicall_entry *mcl, int set)
> >  {
> > diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> > index 5e5c7ae..a33f17e 100644
> > --- a/drivers/xen/privcmd.c
> > +++ b/drivers/xen/privcmd.c
> > @@ -22,6 +22,7 @@
> >  #include <linux/pagemap.h>
> >  #include <linux/seq_file.h>
> >  #include <linux/miscdevice.h>
> > +#include <linux/moduleparam.h>
> >  
> >  #include <asm/pgalloc.h>
> >  #include <asm/pgtable.h>
> > @@ -32,6 +33,7 @@
> >  #include <xen/xen.h>
> >  #include <xen/privcmd.h>
> >  #include <xen/interface/xen.h>
> > +#include <xen/interface/hvm/dm_op.h>
> >  #include <xen/features.h>
> >  #include <xen/page.h>
> >  #include <xen/xen-ops.h>
> > @@ -43,6 +45,17 @@ MODULE_LICENSE("GPL");
> >  
> >  #define PRIV_VMA_LOCKED ((void *)1)
> >  
> > +unsigned int privcmd_dm_op_max_num = 16;
> > +module_param_named(dm_op_max_nr_bufs, privcmd_dm_op_max_num, uint, 0644);
> > +MODULE_PARM_DESC(dm_op_max_nr_bufs,
> > +		 "Maximum number of buffers per dm_op hypercall");
> > +
> > +unsigned int privcmd_dm_op_buf_max_size = XEN_PAGE_SIZE;
> > +module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint,
> > +		   0644);
> > +MODULE_PARM_DESC(dm_op_buf_max_size,
> > +		 "Maximum size of a dm_op hypercall buffer");
> > +
> >  static int privcmd_vma_range_is_mapped(
> >                 struct vm_area_struct *vma,
> >                 unsigned long addr,
> > @@ -548,6 +561,128 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
> >  	goto out;
> >  }
> >  
> > +static int lock_pages(
> > +	struct privcmd_dm_op_buf kbufs[], unsigned int num,
> > +	struct page *pages[], unsigned int nr_pages)
> > +{
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < num; i++) {
> > +		unsigned int requested;
> > +		int pinned;
> > +
> > +		requested = DIV_ROUND_UP(
> > +			offset_in_page(kbufs[i].uptr) + kbufs[i].size,
> > +			PAGE_SIZE);
> > +		if (requested > nr_pages)
> > +			return -ENOSPC;
> > +
> > +		pinned = get_user_pages_fast(
> > +			(unsigned long) kbufs[i].uptr,
> > +			requested, FOLL_WRITE, pages);
> > +		if (pinned < 0)
> > +			return pinned;
> > +
> > +		nr_pages -= pinned;
> > +		pages += pinned;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static void unlock_pages(struct page *pages[], unsigned int nr_pages)
> > +{
> > +	unsigned int i;
> > +
> > +	if (!pages)
> > +		return;
> > +
> > +	for (i = 0; i < nr_pages; i++) {
> > +		if (pages[i])
> > +			put_page(pages[i]);
> > +	}
> > +}
> > +
> > +static long privcmd_ioctl_dm_op(void __user *udata)
> > +{
> > +	struct privcmd_dm_op kdata;
> > +	struct privcmd_dm_op_buf *kbufs;
> > +	unsigned int nr_pages = 0;
> > +	struct page **pages = NULL;
> > +	struct xen_dm_op_buf *xbufs = NULL;
> > +	unsigned int i;
> > +	long rc;
> > +
> > +	if (copy_from_user(&kdata, udata, sizeof(kdata)))
> > +		return -EFAULT;
> > +
> > +	if (kdata.num == 0)
> > +		return 0;
> > +
> > +	if (kdata.num > privcmd_dm_op_max_num)
> > +		return -E2BIG;
> > +
> > +	kbufs = kcalloc(kdata.num, sizeof(*kbufs), GFP_KERNEL);
> > +	if (!kbufs)
> > +		return -ENOMEM;
> > +
> > +	if (copy_from_user(kbufs, kdata.ubufs,
> > +			   sizeof(*kbufs) * kdata.num)) {
> > +		rc = -EFAULT;
> > +		goto out;
> > +	}
> > +
> > +	for (i = 0; i < kdata.num; i++) {
> > +		if (kbufs[i].size > privcmd_dm_op_buf_max_size) {
> > +			rc = -E2BIG;
> > +			goto out;
> > +		}
> > +
> > +		if (!access_ok(VERIFY_WRITE, kbufs[i].uptr,
> > +			       kbufs[i].size)) {
> > +			rc = -EFAULT;
> > +			goto out;
> > +		}
> > +
> > +		nr_pages += DIV_ROUND_UP(
> > +			offset_in_page(kbufs[i].uptr) + kbufs[i].size,
> > +			PAGE_SIZE);
> > +	}
> > +
> > +	pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
> > +	if (!pages) {
> > +		rc = -ENOMEM;
> > +		goto out;
> > +	}
> > +
> > +	xbufs = kcalloc(kdata.num, sizeof(*xbufs), GFP_KERNEL);
> > +	if (!xbufs) {
> > +		rc = -ENOMEM;
> > +		goto out;
> > +	}
> > +
> > +	rc = lock_pages(kbufs, kdata.num, pages, nr_pages);
> > +	if (rc)
> > +		goto out;
> > +
> > +	for (i = 0; i < kdata.num; i++) {
> > +		set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr);
> > +		xbufs[i].size = kbufs[i].size;
> > +	}
> > +
> > +	xen_preemptible_hcall_begin();
> > +	rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
> > +	xen_preemptible_hcall_end();
> > +
> > +out:
> > +	unlock_pages(pages, nr_pages);
> > +	kfree(xbufs);
> > +	kfree(pages);
> > +	kfree(kbufs);
> > +
> > +	return rc;
> > +}
> > +
> >  static long privcmd_ioctl(struct file *file,
> >  			  unsigned int cmd, unsigned long data)
> >  {
> > @@ -571,6 +706,10 @@ static long privcmd_ioctl(struct file *file,
> >  		ret = privcmd_ioctl_mmap_batch(udata, 2);
> >  		break;
> >  
> > +	case IOCTL_PRIVCMD_DM_OP:
> > +		ret = privcmd_ioctl_dm_op(udata);
> > +		break;
> > +
> >  	default:
> >  		break;
> >  	}
> > diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h
> > index 7ddeeda..f8c5d75 100644
> > --- a/include/uapi/xen/privcmd.h
> > +++ b/include/uapi/xen/privcmd.h
> > @@ -77,6 +77,17 @@ struct privcmd_mmapbatch_v2 {
> >  	int __user *err;  /* array of error codes */
> >  };
> >  
> > +struct privcmd_dm_op_buf {
> > +	void __user *uptr;
> > +	size_t size;
> > +};
> > +
> > +struct privcmd_dm_op {
> > +	domid_t dom;
> > +	__u16 num;
> > +	const struct privcmd_dm_op_buf __user *ubufs;
> > +};
> > +
> >  /*
> >   * @cmd: IOCTL_PRIVCMD_HYPERCALL
> >   * @arg: &privcmd_hypercall_t
> > @@ -98,5 +109,7 @@ struct privcmd_mmapbatch_v2 {
> >  	_IOC(_IOC_NONE, 'P', 3, sizeof(struct privcmd_mmapbatch))
> >  #define IOCTL_PRIVCMD_MMAPBATCH_V2				\
> >  	_IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2))
> > +#define IOCTL_PRIVCMD_DM_OP					\
> > +	_IOC(_IOC_NONE, 'P', 5, sizeof(struct privcmd_dm_op))
> >  
> >  #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
> > diff --git a/include/xen/arm/hypercall.h b/include/xen/arm/hypercall.h
> > index 9d874db..73db4b2 100644
> > --- a/include/xen/arm/hypercall.h
> > +++ b/include/xen/arm/hypercall.h
> > @@ -53,6 +53,7 @@ int HYPERVISOR_physdev_op(int cmd, void *arg);
> >  int HYPERVISOR_vcpu_op(int cmd, int vcpuid, void *extra_args);
> >  int HYPERVISOR_tmem_op(void *arg);
> >  int HYPERVISOR_vm_assist(unsigned int cmd, unsigned int type);
> > +int HYPERVISOR_dm_op(domid_t domid, unsigned int nr_bufs, void *bufs);
> >  int HYPERVISOR_platform_op_raw(void *arg);
> >  static inline int HYPERVISOR_platform_op(struct xen_platform_op *op)
> >  {
> > diff --git a/include/xen/interface/hvm/dm_op.h b/include/xen/interface/hvm/dm_op.h
> > new file mode 100644
> > index 0000000..ee9e480
> > --- /dev/null
> > +++ b/include/xen/interface/hvm/dm_op.h
> > @@ -0,0 +1,32 @@
> > +/*
> > + * Copyright (c) 2016, Citrix Systems Inc
> > + *
> > + * Permission is hereby granted, free of charge, to any person obtaining a copy
> > + * of this software and associated documentation files (the "Software"), to
> > + * deal in the Software without restriction, including without limitation the
> > + * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
> > + * sell copies of the Software, and to permit persons to whom the Software is
> > + * furnished to do so, subject to the following conditions:
> > + *
> > + * The above copyright notice and this permission notice shall be included in
> > + * all copies or substantial portions of the Software.
> > + *
> > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> > + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> > + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
> > + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> > + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> > + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> > + * DEALINGS IN THE SOFTWARE.
> > + */
> > +
> > +#ifndef __XEN_PUBLIC_HVM_DM_OP_H__
> > +#define __XEN_PUBLIC_HVM_DM_OP_H__
> > +
> > +struct xen_dm_op_buf {
> > +	GUEST_HANDLE(void) h;
> > +	xen_ulong_t size;
> > +};
> > +DEFINE_GUEST_HANDLE_STRUCT(xen_dm_op_buf);
> > +
> > +#endif /* __XEN_PUBLIC_HVM_DM_OP_H__ */
> > diff --git a/include/xen/interface/xen.h b/include/xen/interface/xen.h
> > index 1b0d189..4f4830e 100644
> > --- a/include/xen/interface/xen.h
> > +++ b/include/xen/interface/xen.h
> > @@ -81,6 +81,7 @@
> >  #define __HYPERVISOR_tmem_op              38
> >  #define __HYPERVISOR_xc_reserved_op       39 /* reserved for XenClient */
> >  #define __HYPERVISOR_xenpmu_op            40
> > +#define __HYPERVISOR_dm_op                41
> >  
> >  /* Architecture-specific hypercall definitions. */
> >  #define __HYPERVISOR_arch_0               48
> 

RE: [PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

[Paul Durrant]

> -----Original Message-----
> From: Stefano Stabellini [mailto:sstabellini@kernel.org]
> Sent: 14 February 2017 18:39
> To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: Paul Durrant <Paul.Durrant@citrix.com>; xen-devel@lists.xenproject.org;
> linux-kernel@vger.kernel.org; Stefano Stabellini <sstabellini@kernel.org>;
> Juergen Gross <jgross@suse.com>
> Subject: Re: [PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP
> 
> On Tue, 14 Feb 2017, Boris Ostrovsky wrote:
> > On 02/13/2017 12:03 PM, Paul Durrant wrote:
> > > Recently a new dm_op[1] hypercall was added to Xen to provide a
> mechanism
> > > for restricting device emulators (such as QEMU) to a limited set of
> > > hypervisor operations, and being able to audit those operations in the
> > > kernel of the domain in which they run.
> > >
> > > This patch adds IOCTL_PRIVCMD_DM_OP as gateway for
> __HYPERVISOR_dm_op.
> > >
> > > NOTE: There is no requirement for user-space code to bounce data
> through
> > >       locked memory buffers (as with IOCTL_PRIVCMD_HYPERCALL) since
> > >       privcmd has enough information to lock the original buffers
> > >       directly.
> > >
> > > [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=524a98c2
> > >
> > > Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> >
> >
> > Stefano,
> >
> > Are you OK with ARM changes?
> 
> Yes:
> 
> Acked-by: Stefano Stabellini <sstabellini@kernel.org>
> 
> Thanks for CC'ing me, I missed the patch.
> 

Sorry. My fault for nor re-running get-maintaner.pl after fixing up the ARM build.

  Paul

Re: [PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

[Boris Ostrovsky]

On 02/13/2017 12:03 PM, Paul Durrant wrote:
> Recently a new dm_op[1] hypercall was added to Xen to provide a mechanism
> for restricting device emulators (such as QEMU) to a limited set of
> hypervisor operations, and being able to audit those operations in the
> kernel of the domain in which they run.
>
> This patch adds IOCTL_PRIVCMD_DM_OP as gateway for __HYPERVISOR_dm_op.
>
> NOTE: There is no requirement for user-space code to bounce data through
>       locked memory buffers (as with IOCTL_PRIVCMD_HYPERCALL) since
>       privcmd has enough information to lock the original buffers
>       directly.
>
> [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=524a98c2
>
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>

Applied to for-linus-4.11 (with agreed upon adjustments)

-boris

[PATCH v3 3/3] xen/privcmd: add IOCTL_PRIVCMD_RESTRICT

[Paul Durrant]

The purpose if this ioctl is to allow a user of privcmd to restrict its
operation such that it will no longer service arbitrary hypercalls via
IOCTL_PRIVCMD_HYPERCALL, and will check for a matching domid when
servicing IOCTL_PRIVCMD_DM_OP. The aim of this is to limit the attack
surface for a compromised device model.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
---
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>

v3:
- Extend restriction to mapping ioctls

v2:
- Make sure that a restriction cannot be cleared
---
 drivers/xen/privcmd.c      | 88 +++++++++++++++++++++++++++++++++++++++++-----
 include/uapi/xen/privcmd.h |  2 ++
 2 files changed, 81 insertions(+), 9 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index a33f17e..f50d984 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -56,16 +56,25 @@ module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint,
 MODULE_PARM_DESC(dm_op_buf_max_size,
 		 "Maximum size of a dm_op hypercall buffer");
 
+struct privcmd_data {
+	domid_t domid;
+};
+
 static int privcmd_vma_range_is_mapped(
                struct vm_area_struct *vma,
                unsigned long addr,
                unsigned long nr_pages);
 
-static long privcmd_ioctl_hypercall(void __user *udata)
+static long privcmd_ioctl_hypercall(struct file *file, void __user *udata)
 {
+	struct privcmd_data *data = file->private_data;
 	struct privcmd_hypercall hypercall;
 	long ret;
 
+	/* Disallow arbitrary hypercalls if restricted */
+	if (data->domid != DOMID_INVALID)
+		return -EPERM;
+
 	if (copy_from_user(&hypercall, udata, sizeof(hypercall)))
 		return -EFAULT;
 
@@ -242,8 +251,9 @@ static int mmap_gfn_range(void *data, void *state)
 	return 0;
 }
 
-static long privcmd_ioctl_mmap(void __user *udata)
+static long privcmd_ioctl_mmap(struct file *file, void __user *udata)
 {
+	struct privcmd_data *data = file->private_data;
 	struct privcmd_mmap mmapcmd;
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
@@ -258,6 +268,10 @@ static long privcmd_ioctl_mmap(void __user *udata)
 	if (copy_from_user(&mmapcmd, udata, sizeof(mmapcmd)))
 		return -EFAULT;
 
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != mmapcmd.dom)
+		return -EPERM;
+
 	rc = gather_array(&pagelist,
 			  mmapcmd.num, sizeof(struct privcmd_mmap_entry),
 			  mmapcmd.entry);
@@ -429,8 +443,10 @@ static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs)
 
 static const struct vm_operations_struct privcmd_vm_ops;
 
-static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
+static long privcmd_ioctl_mmap_batch(
+	struct file *file, void __user *udata, int version)
 {
+	struct privcmd_data *data = file->private_data;
 	int ret;
 	struct privcmd_mmapbatch_v2 m;
 	struct mm_struct *mm = current->mm;
@@ -459,6 +475,10 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
 		return -EINVAL;
 	}
 
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != m.dom)
+		return -EPERM;
+
 	nr_pages = DIV_ROUND_UP(m.num, XEN_PFN_PER_PAGE);
 	if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
 		return -EINVAL;
@@ -603,8 +623,9 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages)
 	}
 }
 
-static long privcmd_ioctl_dm_op(void __user *udata)
+static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
 {
+	struct privcmd_data *data = file->private_data;
 	struct privcmd_dm_op kdata;
 	struct privcmd_dm_op_buf *kbufs;
 	unsigned int nr_pages = 0;
@@ -616,6 +637,10 @@ static long privcmd_ioctl_dm_op(void __user *udata)
 	if (copy_from_user(&kdata, udata, sizeof(kdata)))
 		return -EFAULT;
 
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
+		return -EPERM;
+
 	if (kdata.num == 0)
 		return 0;
 
@@ -683,6 +708,23 @@ static long privcmd_ioctl_dm_op(void __user *udata)
 	return rc;
 }
 
+static long privcmd_ioctl_restrict(struct file *file, void __user *udata)
+{
+	struct privcmd_data *data = file->private_data;
+	domid_t dom;
+
+	if (copy_from_user(&dom, udata, sizeof(dom)))
+		return -EFAULT;
+
+	/* Set restriction to the specified domain, or check it matches */
+	if (data->domid == DOMID_INVALID)
+		data->domid = dom;
+	else if (data->domid != dom)
+		return -EINVAL;
+
+	return 0;
+}
+
 static long privcmd_ioctl(struct file *file,
 			  unsigned int cmd, unsigned long data)
 {
@@ -691,23 +733,27 @@ static long privcmd_ioctl(struct file *file,
 
 	switch (cmd) {
 	case IOCTL_PRIVCMD_HYPERCALL:
-		ret = privcmd_ioctl_hypercall(udata);
+		ret = privcmd_ioctl_hypercall(file, udata);
 		break;
 
 	case IOCTL_PRIVCMD_MMAP:
-		ret = privcmd_ioctl_mmap(udata);
+		ret = privcmd_ioctl_mmap(file, udata);
 		break;
 
 	case IOCTL_PRIVCMD_MMAPBATCH:
-		ret = privcmd_ioctl_mmap_batch(udata, 1);
+		ret = privcmd_ioctl_mmap_batch(file, udata, 1);
 		break;
 
 	case IOCTL_PRIVCMD_MMAPBATCH_V2:
-		ret = privcmd_ioctl_mmap_batch(udata, 2);
+		ret = privcmd_ioctl_mmap_batch(file, udata, 2);
 		break;
 
 	case IOCTL_PRIVCMD_DM_OP:
-		ret = privcmd_ioctl_dm_op(udata);
+		ret = privcmd_ioctl_dm_op(file, udata);
+		break;
+
+	case IOCTL_PRIVCMD_RESTRICT:
+		ret = privcmd_ioctl_restrict(file, udata);
 		break;
 
 	default:
@@ -717,6 +763,28 @@ static long privcmd_ioctl(struct file *file,
 	return ret;
 }
 
+static int privcmd_open(struct inode *ino, struct file *file)
+{
+	struct privcmd_data *data = kzalloc(sizeof(*data), GFP_KERNEL);
+
+	if (!data)
+		return -ENOMEM;
+
+	/* DOMID_INVALID implies no restriction */
+	data->domid = DOMID_INVALID;
+
+	file->private_data = data;
+	return 0;
+}
+
+static int privcmd_release(struct inode *ino, struct file *file)
+{
+	struct privcmd_data *data = file->private_data;
+
+	kfree(data);
+	return 0;
+}
+
 static void privcmd_close(struct vm_area_struct *vma)
 {
 	struct page **pages = vma->vm_private_data;
@@ -785,6 +853,8 @@ static int privcmd_vma_range_is_mapped(
 const struct file_operations xen_privcmd_fops = {
 	.owner = THIS_MODULE,
 	.unlocked_ioctl = privcmd_ioctl,
+	.open = privcmd_open,
+	.release = privcmd_release,
 	.mmap = privcmd_mmap,
 };
 EXPORT_SYMBOL_GPL(xen_privcmd_fops);
diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h
index f8c5d75..63ee95c 100644
--- a/include/uapi/xen/privcmd.h
+++ b/include/uapi/xen/privcmd.h
@@ -111,5 +111,7 @@ struct privcmd_dm_op {
 	_IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2))
 #define IOCTL_PRIVCMD_DM_OP					\
 	_IOC(_IOC_NONE, 'P', 5, sizeof(struct privcmd_dm_op))
+#define IOCTL_PRIVCMD_RESTRICT					\
+	_IOC(_IOC_NONE, 'P', 6, sizeof(domid_t))
 
 #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
-- 
2.1.4

Re: [PATCH v3 3/3] xen/privcmd: add IOCTL_PRIVCMD_RESTRICT

[Boris Ostrovsky]

On 02/13/2017 12:03 PM, Paul Durrant wrote:
> The purpose if this ioctl is to allow a user of privcmd to restrict its
> operation such that it will no longer service arbitrary hypercalls via
> IOCTL_PRIVCMD_HYPERCALL, and will check for a matching domid when
> servicing IOCTL_PRIVCMD_DM_OP.

and IOCTL_PRIVCMD_MMAP*.

> The aim of this is to limit the attack
> surface for a compromised device model.


-boris

Re: [PATCH v3 3/3] xen/privcmd: add IOCTL_PRIVCMD_RESTRICT

[Boris Ostrovsky]

On 02/13/2017 12:03 PM, Paul Durrant wrote:
> The purpose if this ioctl is to allow a user of privcmd to restrict its
> operation such that it will no longer service arbitrary hypercalls via
> IOCTL_PRIVCMD_HYPERCALL, and will check for a matching domid when
> servicing IOCTL_PRIVCMD_DM_OP. The aim of this is to limit the attack
> surface for a compromised device model.
>
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>


Applied to for-linus-4.11 (with commit message adjustment)

-boris