From: Cássio Gabriel Date: Thu, 7 May 2026 03:40:52 +0000 (-0300) Subject: ALSA: usb-audio: Bound MIDI 2.0 endpoint descriptor scans X-Git-Tag: v7.1-rc4~11^2~15 X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=918be519c7876329e1b6e2ea1c59f0b75e792dca;p=thirdparty%2Fkernel%2Flinux.git ALSA: usb-audio: Bound MIDI 2.0 endpoint descriptor scans The USB MIDI 2.0 endpoint parser has the same descriptor walking pattern as the legacy MIDI parser. It validates bLength against bNumGrpTrmBlock before reading baAssoGrpTrmBlkID[], but not against the remaining bytes in the endpoint-extra scan. A malformed device can therefore make later baAssoGrpTrmBlkID[] reads consume bytes past the walked descriptor. Reject zero-length and overlong descriptors while walking endpoint extras. Fixes: ff49d1df79ae ("ALSA: usb-audio: USB MIDI 2.0 UMP support") Cc: stable@vger.kernel.org Signed-off-by: Cássio Gabriel Link: https://patch.msgid.link/20260507-usb-midi-endpoint-scan-bounds-v1-2-329d7348160e@gmail.com Signed-off-by: Takashi Iwai --- diff --git a/sound/usb/midi2.c b/sound/usb/midi2.c index 2785600d23124..04aeb9052f139 100644 --- a/sound/usb/midi2.c +++ b/sound/usb/midi2.c @@ -496,15 +496,17 @@ static void *find_usb_ms_endpoint_descriptor(struct usb_host_endpoint *hostep, while (extralen > 3) { struct usb_ms_endpoint_descriptor *ms_ep = (struct usb_ms_endpoint_descriptor *)extra; + int length = ms_ep->bLength; - if (ms_ep->bLength > 3 && + if (!length || length > extralen) + break; + + if (length > 3 && ms_ep->bDescriptorType == USB_DT_CS_ENDPOINT && ms_ep->bDescriptorSubtype == subtype) return ms_ep; - if (!extra[0]) - break; - extralen -= extra[0]; - extra += extra[0]; + extralen -= length; + extra += length; } return NULL; }