From: Sonali Pradhan Date: Tue, 28 Jul 2026 20:17:16 +0000 (+0000) Subject: ALSA: usb-audio: Fix DMA buffer out-of-bounds write when fill_max is set X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d0199ae1666ff9ae2d1d568d64c3430d4c47f0e5;p=thirdparty%2Flinux.git ALSA: usb-audio: Fix DMA buffer out-of-bounds write when fill_max is set When a USB audio endpoint requests full packet transfers via the fill_max descriptor flag, data_ep_set_params() promotes ep->curpacksize to ep->maxpacksize. However, maxsize is left at the original sample-rate derived value. Since u->buffer_size is allocated as maxsize * packets, the resulting DMA buffer is far too small for the requested transfer length. When the USB host controller streams up to curpacksize bytes per packet, it writes past the end of the buffer via DMA, corrupting kernel heap memory. Update maxsize to curpacksize when fill_max is set so that the allocated DMA buffer size matches the actual transfer request size. [ changed to reassign maxsize only when ep->fill_max is set -- tiwai ] Fixes: 8fdff6a319e7 ("ALSA: snd-usb: implement new endpoint streaming model") Cc: stable@vger.kernel.org Assisted-by: Jetski:Gemini-3.6-Flash Signed-off-by: Sonali Pradhan Link: https://patch.msgid.link/20260728201716.2347726-1-sonalipradhan@google.com Signed-off-by: Takashi Iwai --- diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index 24cd7692bd01..91611d0a4e48 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -1168,10 +1168,12 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep) << (16 - ep->datainterval); } - if (ep->fill_max) + if (ep->fill_max) { ep->curpacksize = ep->maxpacksize; - else + maxsize = ep->curpacksize; + } else { ep->curpacksize = maxsize; + } if (snd_usb_get_speed(chip->dev) != USB_SPEED_FULL) { packs_per_ms = 8 >> ep->datainterval;