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Revert "drm/vmwgfx: Use dma_buf from GEM object instance"

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This reverts commit aec8a40228.

The dma_buf field in struct drm_gem_object is not stable over the
object instance's lifetime. The field becomes NULL when user space
releases the final GEM handle on the buffer object. This resulted
in a NULL-pointer deref.

Workarounds in commit 5307dce878 ("drm/gem: Acquire references on
GEM handles for framebuffers") and commit f6bfc9afc7 ("drm/framebuffer:
Acquire internal references on GEM handles") only solved the problem
partially. They especially don't work for buffer objects without a DRM
framebuffer associated.

Hence, this revert to going back to using .import_attach->dmabuf.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Zack Rusin <zack.rusin@broadcom.com>
Link: https://lore.kernel.org/r/20250715155934.150656-3-tzimmermann@suse.de
This commit is contained in:
Thomas Zimmermann 2025-07-15 17:58:12 +02:00
parent 0ecfb8ddb9
commit 1e9d2aed7c
1 changed files with 3 additions and 3 deletions
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6
drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
View file

@ -85,10 +85,10 @@ static int vmw_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
int ret;
if (drm_gem_is_imported(obj)) {
ret = dma_buf_vmap(obj->dma_buf, map);
ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
if (!ret) {
if (drm_WARN_ON(obj->dev, map->is_iomem)) {
dma_buf_vunmap(obj->dma_buf, map);
dma_buf_vunmap(obj->import_attach->dmabuf, map);
return -EIO;
}
}
@ -102,7 +102,7 @@ static int vmw_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
static void vmw_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map)
{
if (drm_gem_is_imported(obj))
dma_buf_vunmap(obj->dma_buf, map);
dma_buf_vunmap(obj->import_attach->dmabuf, map);
else
drm_gem_ttm_vunmap(obj, map);
}