From: Edward Adam Davis Date: Tue, 13 Jan 2026 08:29:23 +0000 (+0800) Subject: ALSA: usb-audio: Prevent excessive number of frames X-Git-Tag: v6.19-rc6~25^2~3 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ef5749ef8b307bf8717945701b1b79d036af0a15;p=thirdparty%2Flinux.git ALSA: usb-audio: Prevent excessive number of frames In this case, the user constructed the parameters with maxpacksize 40 for rate 22050 / pps 1000, and packsize[0] 22 packsize[1] 23. The buffer size for each data URB is maxpacksize * packets, which in this example is 40 * 6 = 240; When the user performs a write operation to send audio data into the ALSA PCM playback stream, the calculated number of frames is packsize[0] * packets = 264, which exceeds the allocated URB buffer size, triggering the out-of-bounds (OOB) issue reported by syzbot [1]. Added a check for the number of single data URB frames when calculating the number of frames to prevent [1]. [1] BUG: KASAN: slab-out-of-bounds in copy_to_urb+0x261/0x460 sound/usb/pcm.c:1487 Write of size 264 at addr ffff88804337e800 by task syz.0.17/5506 Call Trace: copy_to_urb+0x261/0x460 sound/usb/pcm.c:1487 prepare_playback_urb+0x953/0x13d0 sound/usb/pcm.c:1611 prepare_outbound_urb+0x377/0xc50 sound/usb/endpoint.c:333 Reported-by: syzbot+6db0415d6d5c635f72cb@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6db0415d6d5c635f72cb Tested-by: syzbot+6db0415d6d5c635f72cb@syzkaller.appspotmail.com Signed-off-by: Edward Adam Davis Link: https://patch.msgid.link/tencent_9AECE6CD2C7A826D902D696C289724E8120A@qq.com Signed-off-by: Takashi Iwai --- diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c index 54d01dfd820f..263abb36bb2d 100644 --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -1553,7 +1553,7 @@ static int prepare_playback_urb(struct snd_usb_substream *subs, for (i = 0; i < ctx->packets; i++) { counts = snd_usb_endpoint_next_packet_size(ep, ctx, i, avail); - if (counts < 0) + if (counts < 0 || frames + counts >= ep->max_urb_frames) break; /* set up descriptor */ urb->iso_frame_desc[i].offset = frames * stride;