CVE-2024-50175 — media: qcom: camss: Remove use_count guard in stop_streaming

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

media: qcom: camss: Remove use_count guard in stop_streaming

The use_count check was introduced so that multiple concurrent Raw Data Interfaces RDIs could be driven by different virtual channels VCs on the CSIPHY input driving the video pipeline.

This is an invalid use of use_count though as use_count pertains to the number of times a video entity has been opened by user-space not the number of active streams.

If use_count and stream-on count don't agree then stop_streaming() will break as is currently the case and has become apparent when using CAMSS with libcamera's released softisp 0.3.

The use of use_count like this is a bit hacky and right now breaks regular usage of CAMSS for a single stream case. Stopping qcam results in the splat below, and then it cannot be started again and any attempts to do so fails with -EBUSY.

[ 1265.509831] WARNING: CPU: 5 PID: 919 at drivers/media/common/videobuf2/videobuf2-core.c:2183 __vb2_queue_cancel+0x230/0x2c8 [videobuf2_common] ... [ 1265.510630] Call trace: [ 1265.510636] __vb2_queue_cancel+0x230/0x2c8 [videobuf2_common] [ 1265.510648] vb2_core_streamoff+0x24/0xcc [videobuf2_common] [ 1265.510660] vb2_ioctl_streamoff+0x5c/0xa8 [videobuf2_v4l2] [ 1265.510673] v4l_streamoff+0x24/0x30 [videodev] [ 1265.510707] __video_do_ioctl+0x190/0x3f4 [videodev] [ 1265.510732] video_usercopy+0x304/0x8c4 [videodev] [ 1265.510757] video_ioctl2+0x18/0x34 [videodev] [ 1265.5…

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CVE-2024-50175 — media: qcom: camss: Remove use_count guard in stop_streaming