Re: [PATCH] [media] xc4000: Fix atomicity violation in xc4000_get_frequency

[Greg KH]

On Thu, Dec 21, 2023 at 06:37:07PM +0800, Gui-Dong Han wrote:
> 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. 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.
> 
> Fixes: 4c07e32884ab6 ("[media] xc4000: Fix get_frequency()")
> Reported-by: BassCheck <bass@xxxxxxxxxxx>
> Signed-off-by: Gui-Dong Han <2045gemini@xxxxxxxxx>
> ---
>  drivers/media/tuners/xc4000.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
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created.  Hopefully you will not take offence and will fix the problem
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