[PATCH 0/4 v2] Implement access checks in iommu page fault paths

[PATCH 0/4 v2] Implement access checks in iommu page fault paths

[Joerg Roedel]

Hi,

here is the second version of the patch-set to implement
proper access checks into the io-page-fault handlers of the
AMD IOMMU and Intel VT-d drivers.

Two additional patches clean up the AMD part a bit further.
Since I can't test this this code myself due to lack of
hardware or software that utilizes it, I'd appreciate some
external testing.

It took me a while to get these out, mostly because I tried
to setup my own HSA test environment to at least test the
AMD changes myself. That failed, so I am sending this out
with another request for testing.

Oded, Jesse, would you two please test these patches and
report back? Thanks a lot!


	Joerg

Changes since v1:

	* Updated the access_error functions based on
	  Linus' feedback
	* Rebased to v4.4-rc1

Joerg Roedel (4):
  iommu/amd: Do proper access checking before calling handle_mm_fault()
  iommu/amd: Correctly set flags for handle_mm_fault call
  iommu/amd: Cleanup error handling in do_fault()
  iommu/vt-d: Do access checks before calling handle_mm_fault()

 drivers/iommu/amd_iommu_v2.c | 54 +++++++++++++++++++++++++++-----------------
 drivers/iommu/intel-svm.c    | 20 ++++++++++++++++
 2 files changed, 53 insertions(+), 21 deletions(-)

-- 
1.9.1

[PATCH 1/4] iommu/amd: Do proper access checking before calling handle_mm_fault()

[Joerg Roedel]

From: Joerg Roedel <jroedel@suse.de>

The handle_mm_fault function expects the caller to do the
access checks. Not doing so and calling the function with
wrong permissions is a bug (catched by a BUG_ON).
So fix this bug by adding proper access checking to the io
page-fault code in the AMD IOMMUv2 driver.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/amd_iommu_v2.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index d21d4ed..7caf2fa 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -494,6 +494,22 @@ static void handle_fault_error(struct fault *fault)
 	}
 }
 
+static bool access_error(struct vm_area_struct *vma, struct fault *fault)
+{
+	unsigned long requested = 0;
+
+	if (fault->flags & PPR_FAULT_EXEC)
+		requested |= VM_EXEC;
+
+	if (fault->flags & PPR_FAULT_READ)
+		requested |= VM_READ;
+
+	if (fault->flags & PPR_FAULT_WRITE)
+		requested |= VM_WRITE;
+
+	return (requested & ~vma->vm_flags) != 0;
+}
+
 static void do_fault(struct work_struct *work)
 {
 	struct fault *fault = container_of(work, struct fault, work);
@@ -516,8 +532,8 @@ static void do_fault(struct work_struct *work)
 		goto out;
 	}
 
-	if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) {
-		/* handle_mm_fault would BUG_ON() */
+	/* Check if we have the right permissions on the vma */
+	if (access_error(vma, fault)) {
 		up_read(&mm->mmap_sem);
 		handle_fault_error(fault);
 		goto out;
-- 
1.9.1

[PATCH 2/4] iommu/amd: Correctly set flags for handle_mm_fault call

[Joerg Roedel]

From: Joerg Roedel <jroedel@suse.de>

Instead of just checking for a write access, calculate the
flags that are passed to handle_mm_fault() more precisly and
use the pre-defined macros.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/amd_iommu_v2.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index 7caf2fa..a7edbd6 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -513,16 +513,20 @@ static bool access_error(struct vm_area_struct *vma, struct fault *fault)
 static void do_fault(struct work_struct *work)
 {
 	struct fault *fault = container_of(work, struct fault, work);
-	struct mm_struct *mm;
 	struct vm_area_struct *vma;
+	unsigned int flags = 0;
+	struct mm_struct *mm;
 	u64 address;
-	int ret, write;
-
-	write = !!(fault->flags & PPR_FAULT_WRITE);
+	int ret;
 
 	mm = fault->state->mm;
 	address = fault->address;
 
+	if (fault->flags & PPR_FAULT_USER)
+		flags |= FAULT_FLAG_USER;
+	if (fault->flags & PPR_FAULT_WRITE)
+		flags |= FAULT_FLAG_WRITE;
+
 	down_read(&mm->mmap_sem);
 	vma = find_extend_vma(mm, address);
 	if (!vma || address < vma->vm_start) {
@@ -539,7 +543,7 @@ static void do_fault(struct work_struct *work)
 		goto out;
 	}
 
-	ret = handle_mm_fault(mm, vma, address, write);
+	ret = handle_mm_fault(mm, vma, address, flags);
 	if (ret & VM_FAULT_ERROR) {
 		/* failed to service fault */
 		up_read(&mm->mmap_sem);
-- 
1.9.1

[PATCH 3/4] iommu/amd: Cleanup error handling in do_fault()

[Joerg Roedel]

From: Joerg Roedel <jroedel@suse.de>

Get rid of the three error paths that look the same and move
error handling to a single place.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/amd_iommu_v2.c | 24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index a7edbd6..6a28b74 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -514,10 +514,10 @@ static void do_fault(struct work_struct *work)
 {
 	struct fault *fault = container_of(work, struct fault, work);
 	struct vm_area_struct *vma;
+	int ret = VM_FAULT_ERROR;
 	unsigned int flags = 0;
 	struct mm_struct *mm;
 	u64 address;
-	int ret;
 
 	mm = fault->state->mm;
 	address = fault->address;
@@ -529,31 +529,23 @@ static void do_fault(struct work_struct *work)
 
 	down_read(&mm->mmap_sem);
 	vma = find_extend_vma(mm, address);
-	if (!vma || address < vma->vm_start) {
+	if (!vma || address < vma->vm_start)
 		/* failed to get a vma in the right range */
-		up_read(&mm->mmap_sem);
-		handle_fault_error(fault);
 		goto out;
-	}
 
 	/* Check if we have the right permissions on the vma */
-	if (access_error(vma, fault)) {
-		up_read(&mm->mmap_sem);
-		handle_fault_error(fault);
+	if (access_error(vma, fault))
 		goto out;
-	}
 
 	ret = handle_mm_fault(mm, vma, address, flags);
-	if (ret & VM_FAULT_ERROR) {
-		/* failed to service fault */
-		up_read(&mm->mmap_sem);
-		handle_fault_error(fault);
-		goto out;
-	}
 
+out:
 	up_read(&mm->mmap_sem);
 
-out:
+	if (ret & VM_FAULT_ERROR)
+		/* failed to service fault */
+		handle_fault_error(fault);
+
 	finish_pri_tag(fault->dev_state, fault->state, fault->tag);
 
 	put_pasid_state(fault->state);
-- 
1.9.1

[PATCH 4/4] iommu/vt-d: Do access checks before calling handle_mm_fault()

[Joerg Roedel]

From: Joerg Roedel <jroedel@suse.de>

Not doing so is a bug and might trigger a BUG_ON in
handle_mm_fault(). So add the proper permission checks
before calling into mm code.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/intel-svm.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index c69e3f9..5046483 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -484,6 +484,23 @@ struct page_req_dsc {
 };
 
 #define PRQ_RING_MASK ((0x1000 << PRQ_ORDER) - 0x10)
+
+static bool access_error(struct vm_area_struct *vma, struct page_req_dsc *req)
+{
+	unsigned long requested = 0;
+
+	if (req->exe_req)
+		requested |= VM_EXEC;
+
+	if (req->rd_req)
+		requested |= VM_READ;
+
+	if (req->wr_req)
+		requested |= VM_WRITE;
+
+	return (requested & ~vma->vm_flags) != 0;
+}
+
 static irqreturn_t prq_event_thread(int irq, void *d)
 {
 	struct intel_iommu *iommu = d;
@@ -539,6 +556,9 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 		if (!vma || address < vma->vm_start)
 			goto invalid;
 
+		if (access_error(vma, req))
+			goto invalid;
+
 		ret = handle_mm_fault(svm->mm, vma, address,
 				      req->wr_req ? FAULT_FLAG_WRITE : 0);
 		if (ret & VM_FAULT_ERROR)
-- 
1.9.1

Re: [PATCH 0/4 v2] Implement access checks in iommu page fault paths

[Oded Gabbay]

On Tue, Nov 17, 2015 at 5:11 PM, Joerg Roedel <joro@8bytes.org> wrote:
> Hi,
>
> here is the second version of the patch-set to implement
> proper access checks into the io-page-fault handlers of the
> AMD IOMMU and Intel VT-d drivers.
>
> Two additional patches clean up the AMD part a bit further.
> Since I can't test this this code myself due to lack of
> hardware or software that utilizes it, I'd appreciate some
> external testing.
>
> It took me a while to get these out, mostly because I tried
> to setup my own HSA test environment to at least test the
> AMD changes myself. That failed, so I am sending this out
> with another request for testing.
>
> Oded, Jesse, would you two please test these patches and
> report back? Thanks a lot!
>
>
>         Joerg
>
> Changes since v1:
>
>         * Updated the access_error functions based on
>           Linus' feedback
>         * Rebased to v4.4-rc1
>
> Joerg Roedel (4):
>   iommu/amd: Do proper access checking before calling handle_mm_fault()
>   iommu/amd: Correctly set flags for handle_mm_fault call
>   iommu/amd: Cleanup error handling in do_fault()
>   iommu/vt-d: Do access checks before calling handle_mm_fault()
>
>  drivers/iommu/amd_iommu_v2.c | 54 +++++++++++++++++++++++++++-----------------
>  drivers/iommu/intel-svm.c    | 20 ++++++++++++++++
>  2 files changed, 53 insertions(+), 21 deletions(-)
>
> --
> 1.9.1
>

Hi Joerg,

I have very limited testing capabilities since I left AMD - I only
have Kaveri (which is kind of obsolete) and I only have a very simple
test utility.

>From what I could check, I didn't see any problems, but this is really
such a very basic check that I don't even want to presume to give a
Tested-by tag. Sorry.

I suggest you talk to AMD people, as they have access to Carrizo H/W
and S/W testing framework.

        Oded

Re: [PATCH 0/4 v2] Implement access checks in iommu page fault paths

[Jesse Barnes]

On 11/17/2015 07:11 AM, Joerg Roedel wrote:
> Hi,
> 
> here is the second version of the patch-set to implement
> proper access checks into the io-page-fault handlers of the
> AMD IOMMU and Intel VT-d drivers.
> 
> Two additional patches clean up the AMD part a bit further.
> Since I can't test this this code myself due to lack of
> hardware or software that utilizes it, I'd appreciate some
> external testing.
> 
> It took me a while to get these out, mostly because I tried
> to setup my own HSA test environment to at least test the
> AMD changes myself. That failed, so I am sending this out
> with another request for testing.
> 
> Oded, Jesse, would you two please test these patches and
> report back? Thanks a lot!

I might be able to find time later this week or next; I have to update
my tree to David's latest bits and rebase my i915 code on top along with
these patches.  Then I can run some of my tests and expand them to try
r/w tests w/o mapping the buffer with the right access mode.

Jesse

Re: [PATCH 4/4] iommu/vt-d: Do access checks before calling handle_mm_fault()

[David Woodhouse]

[-- Attachment #1: Type: text/plain, Size: 656 bytes --]

On Tue, 2015-11-17 at 16:11 +0100, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
> 
> Not doing so is a bug and might trigger a BUG_ON in
> handle_mm_fault(). So add the proper permission checks
> before calling into mm code.
> 
> Signed-off-by: Joerg Roedel <jroedel@suse.de>

Acked-By: David Woodhouse <David.Woodhouse@intel.com>

As noted, I can't test it right now until I've replaced my test
hardware. Certainly looks better than the last version though :)

Thanks.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@intel.com                              Intel Corporation


[-- Attachment #2: smime.p7s --]
[-- Type: application/x-pkcs7-signature, Size: 5691 bytes --]

Re: [PATCH 0/4 v2] Implement access checks in iommu page fault paths

[Joerg Roedel]

Hey Jesse,

On Wed, Nov 18, 2015 at 08:13:56AM -0800, Jesse Barnes wrote:
> 
> I might be able to find time later this week or next; I have to update
> my tree to David's latest bits and rebase my i915 code on top along with
> these patches.  Then I can run some of my tests and expand them to try
> r/w tests w/o mapping the buffer with the right access mode.

Have you found time to run some small tests on this?


Thanks,

	Joerg

Re: [PATCH 4/4] iommu/vt-d: Do access checks before calling handle_mm_fault()

[Joerg Roedel]

On Fri, Nov 20, 2015 at 03:35:53PM +0000, David Woodhouse wrote:
> Acked-By: David Woodhouse <David.Woodhouse@intel.com>
> 
> As noted, I can't test it right now until I've replaced my test
> hardware. Certainly looks better than the last version though :)

Okay, thanks. I applied the series to the iommu tree. Patch 1 and 4 as
fixes, the others the the x86/amd branch.