Re: CVE-2025-39751: ALSA: hda/ca0132: Fix buffer overflow in add_tuning_control

Re: CVE-2025-39751: ALSA: hda/ca0132: Fix buffer overflow in add_tuning_control

[Siddh Raman Pant]

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On Thu, 11 Sep 2025 18:52:52 +0200, Greg Kroah-Hartman wrote:
> ALSA: hda/ca0132: Fix buffer overflow in add_tuning_control
> 
> The 'sprintf' call in 'add_tuning_control' may exceed the 44-byte
> buffer if either string argument is too long. This triggers a compiler
> warning.
> Replaced 'sprintf' with 'snprintf' to limit string lengths to prevent
> overflow.
> 
> The Linux kernel CVE team has assigned CVE-2025-39751 to this issue.

While the change is good for defensive reasons, there isn't actually
any buffer overflow as it is to "fix".

The largest string possible is "Wedge Angle Playback Volume", whose
length is less than 44.

Thanks,
Siddh

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Re: CVE-2025-39751: ALSA: hda/ca0132: Fix buffer overflow in add_tuning_control

[gregkh]

On Mon, Oct 06, 2025 at 07:07:00AM +0000, Siddh Raman Pant wrote:
> On Thu, 11 Sep 2025 18:52:52 +0200, Greg Kroah-Hartman wrote:
> > ALSA: hda/ca0132: Fix buffer overflow in add_tuning_control
> > 
> > The 'sprintf' call in 'add_tuning_control' may exceed the 44-byte
> > buffer if either string argument is too long. This triggers a compiler
> > warning.
> > Replaced 'sprintf' with 'snprintf' to limit string lengths to prevent
> > overflow.
> > 
> > The Linux kernel CVE team has assigned CVE-2025-39751 to this issue.
> 
> While the change is good for defensive reasons, there isn't actually
> any buffer overflow as it is to "fix".
> 
> The largest string possible is "Wedge Angle Playback Volume", whose
> length is less than 44.

Thanks for the info.  What was the compiler warning about then if it
could detect just how big the string would always be as these are static
values?

Should this CVE be rejected?

thanks,

greg k-h

Re: CVE-2025-39751: ALSA: hda/ca0132: Fix buffer overflow in add_tuning_control

[Siddh Raman Pant]

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On Mon, Oct 06 2025 at 13:44:23 +0530, gregkh@linuxfoundation.org
wrote:
> On Mon, Oct 06, 2025 at 07:07:00AM +0000, Siddh Raman Pant wrote:
> > On Thu, 11 Sep 2025 18:52:52 +0200, Greg Kroah-Hartman wrote:
> > > ALSA: hda/ca0132: Fix buffer overflow in add_tuning_control
> > > 
> > > The 'sprintf' call in 'add_tuning_control' may exceed the 44-byte
> > > buffer if either string argument is too long. This triggers a compiler
> > > warning.
> > > Replaced 'sprintf' with 'snprintf' to limit string lengths to prevent
> > > overflow.
> > > 
> > > The Linux kernel CVE team has assigned CVE-2025-39751 to this issue.
> > 
> > While the change is good for defensive reasons, there isn't actually
> > any buffer overflow as it is to "fix".
> > 
> > The largest string possible is "Wedge Angle Playback Volume", whose
> > length is less than 44.
> 
> Thanks for the info.  What was the compiler warning about then if it
> could detect just how big the string would always be as these are static
> values?

Probably a false positive.

GCC docs does say:

	-Wformat-overflow
	-Wformat-overflow=level

	    Warn about calls to formatted input/output functions such 
	    as sprintf and vsprintf that might overflow the
destination
	    buffer. When the exact number of bytes written by a format
	    directive cannot be determined at compile-time it is
	    estimated based on heuristics that depend on the level
	    argument and on optimization. While enabling optimization 
	    will in most cases improve the accuracy of the warning, it
	    may also result in false positives.


> Should this CVE be rejected?

Yes.

Thanks,
Siddh

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Re: CVE-2025-39751: ALSA: hda/ca0132: Fix buffer overflow in add_tuning_control

[gregkh]

On Mon, Oct 06, 2025 at 09:19:42AM +0000, Siddh Raman Pant wrote:
> On Mon, Oct 06 2025 at 13:44:23 +0530, gregkh@linuxfoundation.org
> wrote:
> > On Mon, Oct 06, 2025 at 07:07:00AM +0000, Siddh Raman Pant wrote:
> > > On Thu, 11 Sep 2025 18:52:52 +0200, Greg Kroah-Hartman wrote:
> > > > ALSA: hda/ca0132: Fix buffer overflow in add_tuning_control
> > > > 
> > > > The 'sprintf' call in 'add_tuning_control' may exceed the 44-byte
> > > > buffer if either string argument is too long. This triggers a compiler
> > > > warning.
> > > > Replaced 'sprintf' with 'snprintf' to limit string lengths to prevent
> > > > overflow.
> > > > 
> > > > The Linux kernel CVE team has assigned CVE-2025-39751 to this issue.
> > > 
> > > While the change is good for defensive reasons, there isn't actually
> > > any buffer overflow as it is to "fix".
> > > 
> > > The largest string possible is "Wedge Angle Playback Volume", whose
> > > length is less than 44.
> > 
> > Thanks for the info.  What was the compiler warning about then if it
> > could detect just how big the string would always be as these are static
> > values?
> 
> Probably a false positive.
> 
> GCC docs does say:
> 
> 	-Wformat-overflow
> 	-Wformat-overflow=level
> 
> 	    Warn about calls to formatted input/output functions such 
> 	    as sprintf and vsprintf that might overflow the
> destination
> 	    buffer. When the exact number of bytes written by a format
> 	    directive cannot be determined at compile-time it is
> 	    estimated based on heuristics that depend on the level
> 	    argument and on optimization. While enabling optimization 
> 	    will in most cases improve the accuracy of the warning, it
> 	    may also result in false positives.

I can't seem to duplicate this warning on a newer version of gcc than
the original test used:
	https://lore.kernel.org/oe-kbuild-all/202506100642.95jpuMY1-lkp@intel.com/

But that value of "767" is very specific, which feels odd to me.

> > Should this CVE be rejected?
> 
> Yes.

Ok, will do, but this still seems odd, you should patch your kernel just
to be safe :)

thanks,

greg k-h