CVE-2025-39994

Summary

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

media: tuner: xc5000: Fix use-after-free in xc5000_release

The original code uses cancel_delayed_work() in xc5000_release(), which does not guarantee that the delayed work item timer_sleep has fully completed if it was already running. This leads to use-after-free scenarios where xc5000_release() may free the xc5000_priv while timer_sleep is still active and attempts to dereference the xc5000_priv.

A typical race condition is illustrated below:

CPU 0 (release thread) | CPU 1 (delayed work callback) xc5000_release() | xc5000_do_timer_sleep() cancel_delayed_work() | hybrid_tuner_release_state(priv) | kfree(priv) | | priv = container_of() // UAF

Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the timer_sleep is properly canceled before the xc5000_priv memory is deallocated.

A deadlock concern was considered: xc5000_release() is called in a process context and is not holding any locks that the timer_sleep work item might also need. Therefore, the use of the _sync() variant is safe here.

This bug was initially identified through static analysis.

[hverkuil: fix typo in Subject: tunner -> tuner]

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/bc4ffd962ce16a154c44c68853b9d93f5b6fc4b8
• https://git.kernel.org/stable/c/e2f5eaafc0306a76fb1cb760aae804b065b8a341
• https://git.kernel.org/stable/c/3f876cd47ed8bca1e28d68435845949f51f90703
• https://git.kernel.org/stable/c/df0303b4839520b84d9367c2fad65b13650a4d42
• https://git.kernel.org/stable/c/71ed8b81a4906cb785966910f39cf7f5ad60a69e
• https://git.kernel.org/stable/c/effb1c19583bca7022fa641a70766de45c6d41ac
• https://git.kernel.org/stable/c/9a00de20ed8ba90888479749b87bc1532cded4ce
• https://git.kernel.org/stable/c/4266f012806fc18e46da4a04d130df59a4946f93
• https://git.kernel.org/stable/c/40b7a19f321e65789612ebaca966472055dab48c

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