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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@vmware.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@yahoo.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
[bwh: Backported to 3.2: drm_vma_node_start() is open-coded;
vma_pages() was open-coded]
Signed-off-by: Ben Hutchings <ben@decadent.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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