[PATCH 4.9 085/118] drm/i915: Relax mmap VMA check

From: Greg Kroah-Hartman
Date: Fri Mar 22 2019 - 07:45:00 EST

4.9-stable review patch. If anyone has any objections, please let me know.


[ Upstream commit ca22f32a6296cbfa29de56328c8505560a18cfa8 ]

Legacy behaviour was to allow non-page-aligned mmap requests, as does the
linux mmap(2) implementation by virtue of automatically rounding up for
the caller.

To avoid breaking legacy userspace relax the newly introduced fix.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Fixes: 5c4604e757ba ("drm/i915: Prevent a race during I915_GEM_MMAP ioctl with WC set")
Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: Adam Zabrocki <adamza@xxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.0+
Cc: Akash Goel <akash.goel@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20190305110409.28633-1-tvrtko.ursulin@xxxxxxxxxxxxxxx
(cherry picked from commit a90e1948efb648f567444f87f3c19b2a0787affd)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/gpu/drm/i915/i915_gem.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1600,7 +1600,8 @@ __vma_matches(struct vm_area_struct *vma
if (vma->vm_file != filp)
return false;

- return vma->vm_start == addr && (vma->vm_end - vma->vm_start) == size;
+ return vma->vm_start == addr &&
+ (vma->vm_end - vma->vm_start) == PAGE_ALIGN(size);