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ALSA: usb-audio: Use the right limit for PCM OOB check

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The recent fix commit for addressing the OOB access of PCM URB data
buffer caused a regression on Behringer UMC2020HD device, resulting in
choppy sound.  The fix used ep->max_urb_frames for the upper limit
check, and this is no right value to be referred.

Use the actual buffer size (ctx->buffer_size) as the upper limit
instead, which also avoids the regression on the device above.

Fixes: ef5749ef8b ("ALSA: usb-audio: Prevent excessive number of frames")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=220997
Link: https://patch.msgid.link/20260121082025.718748-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2026-01-21 09:20:20 +01:00
parent 930e69757b
commit 70b4db7d25
1 changed files with 2 additions and 1 deletions
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3
sound/usb/pcm.c
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@ -1553,7 +1553,8 @@ 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 || frames + counts >= ep->max_urb_frames)
if (counts < 0 ||
(frames + counts) * stride > ctx->buffer_size)
break;
/* set up descriptor */
urb->iso_frame_desc[i].offset = frames * stride;