[SRU][M/J/F][PATCH 0/1] CVE-2024-24861

[Bethany Jamison]

[Impact]

A race condition was found in the Linux kernel's media/xc4000 device driver
in xc4000 xc4000_get_frequency() function. This can result in return value
overflow issue, possibly leading to malfunction or denial of service issue.

media: xc4000: Fix atomicity violation in xc4000_get_frequency

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.

[Fix]

Mantic:	Clean cherry-pick from linux.6.6.y
Jammy:	Mantic patch applied cleanly
Focal:	Mantic patch applied cleanly
Bionic:	fix sent to esm ML
Xenial:	fix sent to esm ML
Trusty:	not going to be fixed by us

[Test Case]

Compile and boot tested.

[Where problems could occur]

This fix affects those who use the Xceive XC4000 "QAM/8VSB single chip
tuner" driver when accessing the frequency value, an issue with this fix
would be visable to the user via unpredicted system behavior or a system
crash.

Gui-Dong Han (1):
  media: xc4000: Fix atomicity violation in xc4000_get_frequency

 drivers/media/tuners/xc4000.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.34.1