Re: [PATCH v2 5.10.y] ALSA: usb-audio: Fix out of bounds reads when finding clock sources

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Dec 05, 2024 at 01:07:58PM +0000, Benoît Sevens wrote:
> From: Takashi Iwai <tiwai@suse.de>
> 
> Upstream commit a3dd4d63eeb452cfb064a13862fb376ab108f6a6
> 
> The current USB-audio driver code doesn't check bLength of each
> descriptor at traversing for clock descriptors.  That is, when a
> device provides a bogus descriptor with a shorter bLength, the driver
> might hit out-of-bounds reads.
> 
> For addressing it, this patch adds sanity checks to the validator
> functions for the clock descriptor traversal.  When the descriptor
> length is shorter than expected, it's skipped in the loop.
> 
> For the clock source and clock multiplier descriptors, we can just
> check bLength against the sizeof() of each descriptor type.
> OTOH, the clock selector descriptor of UAC2 and UAC3 has an array
> of bNrInPins elements and two more fields at its tail, hence those
> have to be checked in addition to the sizeof() check.
> 
> This patch ports the upstream commit a3dd4d63eeb4 to trees that do not
> include the refactoring commit 9ec730052fa2 ("ALSA: usb-audio:
> Refactoring UAC2/3 clock setup code"). That commit provides union
> objects for pointing both UAC2 and UAC3 objects and unifies the clock
> source, selector and multiplier helper functions. This means we need to
> perform the check in each version specific helper function, but on the
> other hand do not need to do version specific union dereferencing in the
> macros and helper functions.
> 
> Reported-by: Benoît Sevens <bsevens@google.com>
> Cc: <stable@vger.kernel.org>
> Link: https://lore.kernel.org/20241121140613.3651-1-bsevens@google.com
> Link: https://patch.msgid.link/20241125144629.20757-1-tiwai@suse.de
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> (cherry picked from commit a3dd4d63eeb452cfb064a13862fb376ab108f6a6)
> Signed-off-by: Benoît Sevens <bsevens@google.com>
> ---
>  sound/usb/clock.c | 32 ++++++++++++++++++++++++++++++--
>  1 file changed, 30 insertions(+), 2 deletions(-)

What changed in v2?