On 27/01/2023 20:05, Rob Clark wrote:
From: Rob Clark <robdclark@xxxxxxxxxxxx>
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.
Fixes: e9b73c67390a ("drm/i915: Reduce memory pressure during shrinker by preallocating swizzle pages")
Should be:
Fixes: 2850748ef876 ("drm/i915: Pull i915_vma_pin under the vm->mutex")
Before that commit there as a "BKL" (struct_mutex) aroung the call to
i915_gem_object_set_tiling. Otherwise fix looks good:
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
I'll tweak the fixes tag and merge in a minute, thanks for the fix!
Regards,
Tvrtko
Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_tiling.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_tiling.c b/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
index fd42b89b7162..bc21b1c2350a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
@@ -298,36 +298,37 @@ i915_gem_object_set_tiling(struct drm_i915_gem_object *obj,
vma->fence_alignment =
i915_gem_fence_alignment(i915,
vma->size, tiling, stride);
if (vma->fence)
vma->fence->dirty = true;
}
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)) {
if (!obj->bit_17) {
obj->bit_17 = bitmap_zalloc(obj->base.size >> PAGE_SHIFT,
GFP_KERNEL);
}
} else {
bitmap_free(obj->bit_17);
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;
}
/**
* i915_gem_set_tiling_ioctl - IOCTL handler to set tiling mode
* @dev: DRM device
* @data: data pointer for the ioctl
* @file: DRM file for the ioctl call
*
* Sets the tiling mode of an object, returning the required swizzling of
