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[ Upstream commit 36d503ad547d1c75758a6fcdbec2806f1b6aeb41 ] In xc4000_get_frequency(): *freq = priv->freq_hz + priv->freq_offset; The code accesses priv->freq_hz and priv->freq_offset without holding any lock. In xc4000_set_params(): // Code that updates priv->freq_hz and priv->freq_offset ... xc4000_get_frequency() and xc4000_set_params() may execute concurrently, risking inconsistent reads of priv->freq_hz and priv->freq_offset. Since these related data may update during reading, it can result in incorrect frequency calculation, leading to atomicity violations. This possible bug is found by an experimental static analysis tool developed by our team, BassCheck[1]. This tool analyzes the locking APIs to extract function pairs that can be concurrently executed, and then analyzes the instructions in the paired functions to identify possible concurrency bugs including data races and atomicity violations. The above possible bug is reported when our tool analyzes the source code of Linux 6.2. To address this issue, it is proposed to add a mutex lock pair in xc4000_get_frequency() to ensure atomicity. With this patch applied, our tool no longer reports the possible bug, with the kernel configuration allyesconfig for x86_64. Due to the lack of associated hardware, we cannot test the patch in runtime testing, and just verify it according to the code logic. [1] https://sites.google.com/view/basscheck/ Fixes: 4c07e32884ab ("[media] xc4000: Fix get_frequency()") Cc: stable@vger.kernel.org Reported-by: BassCheck <bass@buaa.edu.cn> Signed-off-by: Gui-Dong Han <2045gemini@gmail.com> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Sasha Levin <sashal@kernel.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.