virtio_gpu_cursor_plane_update() and virtio_gpu_resource_flush() lock
the framebuffer BO's dma_resv via virtio_gpu_array_lock_resv() and
ignore its return value. The function can fail with -EINTR from
dma_resv_lock_interruptible() (signal during lock wait) or with
-ENOMEM from dma_resv_reserve_fences() (fence slot allocation),
leaving the resv lock not held. The queue path then walks the object
array and calls dma_resv_add_fence(), which requires the lock held;
with lockdep enabled this trips dma_resv_assert_held():
WARNING: drivers/dma-buf/dma-resv.c:296 at dma_resv_add_fence+0x71e/0x840
Call Trace:
virtio_gpu_array_add_fence
virtio_gpu_queue_ctrl_sgs
virtio_gpu_queue_fenced_ctrl_buffer
virtio_gpu_cursor_plane_update
drm_atomic_helper_commit_planes
drm_atomic_helper_commit_tail
commit_tail
drm_atomic_helper_commit
drm_atomic_commit
drm_atomic_helper_update_plane
__setplane_atomic
drm_mode_cursor_universal
drm_mode_cursor_common
drm_mode_cursor_ioctl
drm_ioctl
__x64_sys_ioctl
Beyond the WARN, mutating the dma_resv fence list without the lock
races with concurrent readers/writers and can corrupt the list.
Both call sites run inside the .atomic_update plane callback, which
DRM atomic helpers do not allow to fail (by the time it runs, the
commit has been signed off to userspace and there is no clean
rollback path). Moving the lock acquisition to .prepare_fb was
rejected because the broader lock scope deadlocks against other BO
locking paths in the same atomic commit.
Introduce virtio_gpu_lock_one_resv_uninterruptible() that uses
dma_resv_lock() instead of dma_resv_lock_interruptible(). This
eliminates the -EINTR failure mode -- the realistic syzbot trigger
-- without extending the lock hold across the commit. The helper
locks a single BO and rejects nents > 1 with -EINVAL; both fix
sites lock exactly one BO.
Use it from virtio_gpu_cursor_plane_update() and
virtio_gpu_resource_flush(); check the return value to handle the
remaining -ENOMEM case from dma_resv_reserve_fences() by freeing
the objs and skipping the plane update for that frame. The
framebuffer BOs touched here are not shared with other contexts
and lock contention is expected to be brief, so the loss of
signal-interruptibility is acceptable.
Other callers of virtio_gpu_array_lock_resv() (the ioctl paths)
continue to use the interruptible variant.
The bug was reported by syzbot, triggered via fault injection
(fail_nth) on the DRM_IOCTL_MODE_CURSOR path, which forces the
-ENOMEM branch in dma_resv_reserve_fences().
Reported-by: syzbot+72bd3dd3a5d5f39a0271@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=72bd3dd3a5d5f39a0271
Fixes: 5cfd31c5b3 ("drm/virtio: fix virtio_gpu_cursor_plane_update().")
Cc: stable@vger.kernel.org
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patch.msgid.link/20260519082247.34470-1-kartikey406@gmail.com
This was done entirely with mindless brute force, using
git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'
to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.
Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.
For the same reason the 'flex' versions will be done as a separate
conversion.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
Having a fence linked to a virtio_gpu_framebuffer in the plane update
sequence would cause conflict when several planes referencing the same
framebuffer (e.g. Xorg screen covering multi-displays configured for an
extended mode) and those planes are updated concurrently. So it is needed
to allocate a fence for every plane state instead of the framebuffer.
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
[dmitry.osipenko@collabora.com: rebase, fix up, edit commit message]
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Acked-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241020230803.247419-2-dmitry.osipenko@collabora.com
Use drm_gem_plane_helper_prepare_fb() helper for explicit framebuffer
synchronization. We need to wait for explicit fences in a case of
Venus and native contexts when guest user space uses explicit fencing.
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
[dmitry.osipenko@collabora.com: edit commit message]
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Acked-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241020230803.247419-1-dmitry.osipenko@collabora.com
These were defined in the previous commit. We'll need these
parameters when allocating a dma_fence. The use case for this
is multiple synchronizations timelines.
The maximum number of timelines per 3D instance will be 32. Usually,
only 2 are needed -- one for CPU commands, and another for GPU
commands.
As such, we'll need to specify these parameters when allocating a
dma_fence.
vgdev->fence_drv.context is the "default" fence context for 2D mode
and old userspace.
Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
Acked-by: Lingfeng Yang <lfy@google.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20210921232024.817-8-gurchetansingh@chromium.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
