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Duoming Zhou effb1c1958 media: tuner: xc5000: Fix use-after-free in xc5000_release 
commit 40b7a19f32 upstream.

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.

Fixes: f7a27ff1fb ("[media] xc5000: delay tuner sleep to 5 seconds")
Cc: stable@vger.kernel.org
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
[hverkuil: fix typo in Subject: tunner -> tuner]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-10-06 11:17:52 +02:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.