drm/i915/userptr: Hold mmref whilst calling get-user-pages
authorChris Wilson <chris@chris-wilson.co.uk>
Tue, 5 Apr 2016 14:00:00 +0000 (15:00 +0100)
committerJani Nikula <jani.nikula@intel.com>
Mon, 18 Apr 2016 09:35:49 +0000 (12:35 +0300)
commitdb9f9203e27495b2d151b695504e286eec026e9b
tree2c8d22c693031da6bda1ae7976c60f176cea4e7b
parentd43f3ebf12f59c57782ec652da65ef61c2662b40
drm/i915/userptr: Hold mmref whilst calling get-user-pages

Holding a reference to the containing task_struct is not sufficient to
prevent the mm_struct from being reaped under memory pressure. If this
happens whilst we are calling get_user_pages(), explosions erupt -
sometimes an immediate GPF, sometimes page flag corruption. To prevent
the target mm from being reaped as we are reading from it, acquire a
reference before we begin.

Testcase: igt/gem_shrink/*userptr
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459864801-28606-2-git-send-email-chris@chris-wilson.co.uk
(cherry picked from commit 40313f0cd0b711a7a5905e5182422799e157d8aa)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
drivers/gpu/drm/i915/i915_gem_userptr.c