Description

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]

References 9

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

Remediation