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

media: mtk-jpeg: Fix use after free bug due to error path handling in mtk_jpeg_dec_device_run

In mtk_jpeg_probe, &jpeg->job_timeout_work is bound with
mtk_jpeg_job_timeout_work.

In mtk_jpeg_dec_device_run, if error happens in
mtk_jpeg_set_dec_dst, it will finally start the worker while
mark the job as finished by invoking v4l2_m2m_job_finish.

There are two methods to trigger the bug. If we remove the
module, it which will call mtk_jpeg_remove to make cleanup.
The possible sequence is as follows, which will cause a
use-after-free bug.

CPU0 CPU1
mtk_jpeg_dec_... |
start worker |
|mtk_jpeg_job_timeout_work
mtk_jpeg_remove |
v4l2_m2m_release |
kfree(m2m_dev); |
|
| v4l2_m2m_get_curr_priv
| m2m_dev->curr_ctx //use

If we close the file descriptor, which will call mtk_jpeg_release,
it will have a similar sequence.

Fix this bug by starting timeout worker only if started jpegdec worker
successfully. Then v4l2_m2m_job_finish will only be called in
either mtk_jpeg_job_timeout_work or mtk_jpeg_dec_device_run.

References

• https://nvd.nist.gov/vuln/detail/CVE-2023-52491
• https://git.kernel.org/stable/c/1b1036c60a37a30caf6759a90fe5ecd06ec35590
• https://git.kernel.org/stable/c/206c857dd17d4d026de85866f1b5f0969f2a109e
• https://git.kernel.org/stable/c/43872f44eee6c6781fea1348b38885d8e78face9
• https://git.kernel.org/stable/c/6e2f37022f0fc0893da4d85a0500c9d547fffd4c
• https://git.kernel.org/stable/c/8254d54d00eb6cdb8367399c7f912eb8d354ecd7
• https://git.kernel.org/stable/c/9fec4db7fff54d9b0306a332bab31eac47eeb5f6