6.15-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Zimmermann tzimmermann@suse.de
commit 6d496e9569983a0d7a05be6661126d0702cf94f7 upstream.
This reverts commit 1a148af06000e545e714fe3210af3d77ff903c11.
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 5307dce878d4 ("drm/gem: Acquire references on GEM handles for framebuffers") and commit f6bfc9afc751 ("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.
v3: - cc stable
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 Cc: stable@vger.kernel.org # v6.15+ Link: https://lore.kernel.org/r/20250715155934.150656-7-tzimmermann@suse.de Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/drm_gem_shmem_helper.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -339,7 +339,7 @@ int drm_gem_shmem_vmap(struct drm_gem_sh int ret = 0;
if (drm_gem_is_imported(obj)) { - ret = dma_buf_vmap(obj->dma_buf, map); + ret = dma_buf_vmap(obj->import_attach->dmabuf, map); } else { pgprot_t prot = PAGE_KERNEL;
@@ -399,7 +399,7 @@ void drm_gem_shmem_vunmap(struct drm_gem struct drm_gem_object *obj = &shmem->base;
if (drm_gem_is_imported(obj)) { - dma_buf_vunmap(obj->dma_buf, map); + dma_buf_vunmap(obj->import_attach->dmabuf, map); } else { dma_resv_assert_held(shmem->base.resv);