In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/virtio: use uninterruptible resv lock for plane updates<\/p>\n
virtio_gpu_cursor_plane_update() and virtio_gpu_resource_flush() lock
\nthe framebuffer BO’s dma_resv via virtio_gpu_array_lock_resv() and
\nignore its return value. The function can fail with -EINTR from
\ndma_resv_lock_interruptible() (signal during lock wait) or with
\n-ENOMEM from dma_resv_reserve_fences() (fence slot allocation),
\nleaving the resv lock not held. The queue path then walks the object
\narray and calls dma_resv_add_fence(), which requires the lock held;
\nwith lockdep enabled this trips dma_resv_assert_held():<\/p>\n
WARNING: drivers\/dma-buf\/dma-resv.c:296 at dma_resv_add_fence+0x71e\/0x840
\n Call Trace:
\n virtio_gpu_array_add_fence
\n virtio_gpu_queue_ctrl_sgs
\n virtio_gpu_queue_fenced_ctrl_buffer
\n virtio_gpu_cursor_plane_update
\n drm_atomic_helper_commit_planes
\n drm_atomic_helper_commit_tail
\n commit_tail
\n drm_atomic_helper_commit
\n drm_atomic_commit
\n drm_atomic_helper_update_plane
\n __setplane_atomic
\n drm_mode_cursor_universal
\n drm_mode_cursor_common
\n drm_mode_cursor_ioctl
\n drm_ioctl
\n __x64_sys_ioctl<\/p>\n
Beyond the WARN, mutating the dma_resv fence list without the lock
\nraces with concurrent readers\/writers and can corrupt the list.<\/p>\n
Both call sites run inside the .atomic_update plane callback, which
\nDRM atomic helpers do not allow to fail (by the time it runs, the
\ncommit has been signed off to userspace and there is no clean
\nrollback path). Moving the lock acquisition to .prepare_fb was
\nrejected because the broader lock scope deadlocks against other BO
\nlocking paths in the same atomic commit.<\/p>\n
Introduce virtio_gpu_lock_one_resv_uninterruptible() that uses
\ndma_resv_lock() instead of dma_resv_lock_interruptible(). This
\neliminates the -EINTR failure mode — the realistic syzbot trigger
\n— without extending the lock hold across the commit. The helper
\nlocks a single BO and rejects nents > 1 with -EINVAL; both fix
\nsites lock exactly one BO.<\/p>\n
Use it from virtio_gpu_cursor_plane_update() and
\nvirtio_gpu_resource_flush(); check the return value to handle the
\nremaining -ENOMEM case from dma_resv_reserve_fences() by freeing
\nthe objs and skipping the plane update for that frame. The
\nframebuffer BOs touched here are not shared with other contexts
\nand lock contention is expected to be brief, so the loss of
\nsignal-interruptibility is acceptable.<\/p>\n
Other callers of virtio_gpu_array_lock_resv() (the ioctl paths)
\ncontinue to use the interruptible variant.<\/p>\n
The bug was reported by syzbot, triggered via fault injection
\n(fail_nth) on the DRM_IOCTL_MODE_CURSOR path, which forces the
\n-ENOMEM branch in dma_resv_reserve_fences().<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/virtio: use uninterruptible resv lock for plane updates<\/p>\n
virtio_gpu_cursor_plane_update() and virtio_gpu_resource_flush() lock<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-15072","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/15072","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15072"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=15072"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=15072"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}