diff options
| author | Kieran Bingham <kieran.bingham@ideasonboard.com> | 2021-09-09 16:08:03 +0100 |
|---|---|---|
| committer | Kieran Bingham <kieran.bingham@ideasonboard.com> | 2021-09-14 12:54:45 +0100 |
| commit | 4cf7a8fc0bd5a2c6b606f27101d905f63a846b5f (patch) | |
| tree | 138cd9d3938a3e02be9cbcd03c09ece25b23c247 /src | |
| parent | 3bcb7a90c1b1404e51015bda9add4d2ba467c052 (diff) | |
libcamera: v4l2_videodevice: Handle unexpected buffers
A kernel bug can lead to unexpected buffers being dequeued where we
haven't entered the buffer in our queuedBuffers_ list.
This causes invalid accesses if not handled correctly within libcamera,
and while it is a kernel issue, we can protect against unpatched
kernels to provide a more suitable error message.
This is fixed in the kernel by commit c592b46907ad ("media:
videobuf2-core: dequeue if start_streaming fails") [0]
[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c592b46907ad
Handle unexpected buffers by returning a nullptr, and move cache
management after the validation of the buffer.
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Diffstat (limited to 'src')
| -rw-r--r-- | src/libcamera/v4l2_videodevice.cpp | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp index 837a59d9..9b3ee887 100644 --- a/src/libcamera/v4l2_videodevice.cpp +++ b/src/libcamera/v4l2_videodevice.cpp @@ -1654,9 +1654,28 @@ FrameBuffer *V4L2VideoDevice::dequeueBuffer() LOG(V4L2, Debug) << "Dequeuing buffer " << buf.index; + /* + * If the video node fails to stream-on successfully (which can occur + * when queuing a buffer), a vb2 kernel bug can lead to the buffer which + * returns a failure upon queuing being mistakenly kept in the kernel. + * This leads to the kernel notifying us that a buffer is available to + * dequeue, which we have no awareness of being queued, and thus we will + * not find it in the queuedBuffers_ list. + * + * Whilst this kernel bug has been fixed in mainline, ensure that we + * safely ingore buffers which are unexpected to prevetn crashes on + * older kernels. + */ + auto it = queuedBuffers_.find(buf.index); + if (it == queuedBuffers_.end()) { + LOG(V4L2, Error) + << "Dequeued unexpected buffer index " << buf.index; + + return nullptr; + } + cache_->put(buf.index); - auto it = queuedBuffers_.find(buf.index); FrameBuffer *buffer = it->second; queuedBuffers_.erase(it); |