CVE-2025-39994

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

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

The original code uses canceldelayedwork() in xc5000release(), which does not guarantee that the delayed work item timersleep has fully completed if it was already running. This leads to use-after-free scenarios where xc5000release() may free the xc5000priv while timersleep is still active and attempts to dereference the xc5000priv.

A typical race condition is illustrated below:

CPU 0 (release thread) | CPU 1 (delayed work callback) xc5000release() | xc5000dotimersleep() canceldelayedwork() | hybridtunerreleasestate(priv) | kfree(priv) | | priv = containerof() // UAF

Replace canceldelayedwork() with canceldelayedworksync() to ensure that the timersleep is properly canceled before the xc5000_priv memory is deallocated.

A deadlock concern was considered: xc5000release() is called in a process context and is not holding any locks that the timersleep 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]