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71ed8b81a4
[ Upstream commit 40b7a19f321e65789612ebaca966472055dab48c ]
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: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 Restructured Text 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.