Commit 10e0cbaa authored by Rob Clark's avatar Rob Clark Committed by Tvrtko Ursulin
Browse files

drm/i915: Fix potential bit_17 double-free 



A userspace with multiple threads racing I915_GEM_SET_TILING to set the
tiling to I915_TILING_NONE could trigger a double free of the bit_17
bitmask.  (Or conversely leak memory on the transition to tiled.)  Move
allocation/free'ing of the bitmask within the section protected by the
obj lock.

Signed-off-by: default avatarRob Clark <robdclark@chromium.org>
Fixes: 2850748e ("drm/i915: Pull i915_vma_pin under the vm->mutex")
Cc: <stable@vger.kernel.org> # v5.5+
[tursulin: Correct fixes tag and added cc stable.]
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230127200550.3531984-1-robdclark@gmail.com
parent 583ebae7

drivers/gpu/drm/i915/gem/i915_gem_tiling.c

+5 −4
Original line number Diff line number Diff line
@@ -305,10 +305,6 @@ i915_gem_object_set_tiling(struct drm_i915_gem_object *obj, 
	spin_unlock(&obj->vma.lock);



	obj->tiling_and_stride = tiling | stride;

	i915_gem_object_unlock(obj);



	/* Force the fence to be reacquired for GTT access */

	i915_gem_object_release_mmap_gtt(obj);



	/* Try to preallocate memory required to save swizzling on put-pages */

	if (i915_gem_object_needs_bit17_swizzle(obj)) {
@@ -321,6 +317,11 @@ i915_gem_object_set_tiling(struct drm_i915_gem_object *obj, 
		obj->bit_17 = NULL;

	}



	i915_gem_object_unlock(obj);



	/* Force the fence to be reacquired for GTT access */

	i915_gem_object_release_mmap_gtt(obj);



	return 0;

}