linux-kernel - [PATCH 3.2 45/79] drm/ttm: Fix accesses through vmas with only partial coverage

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Message-ID: <lsq.1392192612.726864176@decadent.org.uk>
Date:	Wed, 12 Feb 2014 08:10:12 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Thomas Hellstrom" <thellstrom@...are.com>,
	"Joseph Dolinak" <kanilo2@...oo.com>,
	"Jakob Bornecrantz" <jakob@...are.com>
Subject: [PATCH 3.2 45/79] drm/ttm: Fix accesses through vmas with only
 partial coverage

3.2.55-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Hellstrom <thellstrom@...are.com>

commit d386735588c3e22129c2bc6eb64fc1d37a8f805c upstream.

VMAs covering a bo but that didn't start at the same address space offset as
the bo they were mapping were incorrectly generating SEGFAULT errors in
the fault handler.

Reported-by: Joseph Dolinak <kanilo2@...oo.com>
Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
Reviewed-by: Jakob Bornecrantz <jakob@...are.com>
[bwh: Backported to 3.2: drm_vma_node_start() is open-coded;
 vma_pages() was open-coded]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/ttm/ttm_bo_vm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -144,9 +144,9 @@ static int ttm_bo_vm_fault(struct vm_are
 	}
 
 	page_offset = ((address - vma->vm_start) >> PAGE_SHIFT) +
-	    bo->vm_node->start - vma->vm_pgoff;
-	page_last = ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) +
-	    bo->vm_node->start - vma->vm_pgoff;
+		vma->vm_pgoff - bo->vm_node->start;
+	page_last = vma_pages(vma) + vma->vm_pgoff -
+		bo->vm_node->start;
 
 	if (unlikely(page_offset >= bo->num_pages)) {
 		retval = VM_FAULT_SIGBUS;

--
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