CVE-2023-52491

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.

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• 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
• 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
• https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html