[libcamera-devel] [PATCH v1 1/2] libcamera: v4l2_videodevice: Guard against releasing unallocated buffers

[Naushir Patuck]

Apologies!  This was not meant to be the patch I wanted to push.  My brain
has shut down for the weekend.
I'll push an update for the correct patch in reply to this one.

Naush



On Fri, 28 Oct 2022 at 12:52, Naushir Patuck <naush at raspberrypi.com> wrote:

> releaseBuffers() unconditionally calls ioctl(REQBUFS, 0) to release device
> buffer allocations through the close() and class destructor functions. If
> another libcamera process is running concurrently with a different sensor,
> it
> would cause the ioctl to fail in the kernel because the buffer queue is
> owned
> owned by the other process. This in turn would cause libcamera to generate
> an
> error log message.
>
> Fix this by ensuring the releaseBuffers() only calls ioctl(REQBUFS, 0) if
> there
> have been buffers previously allocated by the device. This is done by
> testing
> the presense of the V4L2BufferCache in the object.
>
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> ---
>  src/libcamera/v4l2_videodevice.cpp | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/src/libcamera/v4l2_videodevice.cpp
> b/src/libcamera/v4l2_videodevice.cpp
> index e30858c9fa02..ed446c25e45f 100644
> --- a/src/libcamera/v4l2_videodevice.cpp
> +++ b/src/libcamera/v4l2_videodevice.cpp
> @@ -1533,6 +1533,9 @@ int V4L2VideoDevice::importBuffers(unsigned int
> count)
>   */
>  int V4L2VideoDevice::releaseBuffers()
>  {
> +       if (!cache_)
> +               return;
> +
>         LOG(V4L2, Debug) << "Releasing buffers";
>
>         delete cache_;
> --
> 2.25.1
>
>
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