5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Takashi Iwai tiwai@suse.de
commit 05a1fc5efdd8560f34a3af39c9cf1e1526cc3ddf upstream.
The PCM stream data in USB-audio driver is transferred over USB URB packet buffers, and each packet size is determined dynamically. The packet sizes are limited by some factors such as wMaxPacketSize USB descriptor. OTOH, in the current code, the actually used packet sizes are determined only by the rate and the PPS, which may be bigger than the size limit above. This results in a buffer overflow, as reported by syzbot.
Basically when the limit is smaller than the calculated packet size, it implies that something is wrong, most likely a weird USB descriptor. So the best option would be just to return an error at the parameter setup time before doing any further operations.
This patch introduces such a sanity check, and returns -EINVAL when the packet size is greater than maxpacksize. The comparison with ep->packsize[1] alone should suffice since it's always equal or greater than ep->packsize[0].
Reported-by: syzbot+bfd77469c8966de076f7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=bfd77469c8966de076f7 Link: https://lore.kernel.org/690b6b46.050a0220.3d0d33.0054.GAE@google.com Cc: Lizhi Xu lizhi.xu@windriver.com Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20251109091211.12739-1-tiwai@suse.de Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- sound/usb/endpoint.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -1374,6 +1374,11 @@ int snd_usb_endpoint_set_params(struct s ep->sample_rem = ep->cur_rate % ep->pps; ep->packsize[0] = ep->cur_rate / ep->pps; ep->packsize[1] = (ep->cur_rate + (ep->pps - 1)) / ep->pps; + if (ep->packsize[1] > ep->maxpacksize) { + usb_audio_dbg(chip, "Too small maxpacksize %u for rate %u / pps %u\n", + ep->maxpacksize, ep->cur_rate, ep->pps); + return -EINVAL; + }
/* calculate the frequency in 16.16 format */ ep->freqm = ep->freqn;
On Wed, 03 Dec 2025 16:27:06 +0100, Greg Kroah-Hartman wrote:
5.15-stable review patch. If anyone has any objections, please let me know.
From: Takashi Iwai tiwai@suse.de
commit 05a1fc5efdd8560f34a3af39c9cf1e1526cc3ddf upstream.
The PCM stream data in USB-audio driver is transferred over USB URB packet buffers, and each packet size is determined dynamically. The packet sizes are limited by some factors such as wMaxPacketSize USB descriptor. OTOH, in the current code, the actually used packet sizes are determined only by the rate and the PPS, which may be bigger than the size limit above. This results in a buffer overflow, as reported by syzbot.
Basically when the limit is smaller than the calculated packet size, it implies that something is wrong, most likely a weird USB descriptor. So the best option would be just to return an error at the parameter setup time before doing any further operations.
This patch introduces such a sanity check, and returns -EINVAL when the packet size is greater than maxpacksize. The comparison with ep->packsize[1] alone should suffice since it's always equal or greater than ep->packsize[0].
Reported-by: syzbot+bfd77469c8966de076f7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=bfd77469c8966de076f7 Link: https://lore.kernel.org/690b6b46.050a0220.3d0d33.0054.GAE@google.com Cc: Lizhi Xu lizhi.xu@windriver.com Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20251109091211.12739-1-tiwai@suse.de Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
sound/usb/endpoint.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -1374,6 +1374,11 @@ int snd_usb_endpoint_set_params(struct s ep->sample_rem = ep->cur_rate % ep->pps; ep->packsize[0] = ep->cur_rate / ep->pps; ep->packsize[1] = (ep->cur_rate + (ep->pps - 1)) / ep->pps;
- if (ep->packsize[1] > ep->maxpacksize) {
usb_audio_dbg(chip, "Too small maxpacksize %u for rate %u / pps %u\n",ep->maxpacksize, ep->cur_rate, ep->pps);return -EINVAL;- }
/* calculate the frequency in 16.16 format */ ep->freqm = ep->freqn;
This backport requires a similar workaround done for 6.12.y for the unbalanced mutex lock, the downstream commit fdf0dc82eb60 ALSA: usb-audio: Fix missing unlock at error path of maxpacksize check
It seems that 5.10.y doesn't need the workaround as it has no mutex lock applied around it.
thanks,
Takashi
linux-stable-mirror@lists.linaro.org
-
Greg Kroah-Hartman -
Takashi Iwai