drm/i915: Prevent a race during I915_GEM_MMAP ioctl with WC set
Make sure the underlying VMA in the process address space is the same as it was during vm_mmap to avoid applying WC to wrong VMA. A more long-term solution would be to have vm_mmap_locked variant in linux/mmap.h for when caller wants to hold mmap_sem for an extended duration. v2: - Refactor the compare function Fixes: 1816f923 ("drm/i915: Support creation of unbound wc user mappings for objects") Reported-by: NAdam Zabrocki <adamza@microsoft.com> Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org> Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: <stable@vger.kernel.org> # v4.0+ Cc: Akash Goel <akash.goel@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> Cc: Adam Zabrocki <adamza@microsoft.com> Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> #v1 Link: https://patchwork.freedesktop.org/patch/msgid/20190207085454.10598-1-joonas.lahtinen@linux.intel.com (cherry picked from commit 5c4604e7) Signed-off-by: NJani Nikula <jani.nikula@intel.com>
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