From d6854daa67be623860f4e1873fd3d3c275aba4ed Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?C=C3=A1ssio=20Gabriel?= Date: Thu, 7 May 2026 00:40:51 -0300 Subject: [PATCH] ALSA: usb-audio: Bound MIDI endpoint descriptor scans MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit snd_usbmidi_get_ms_info() validates the internal MIDIStreaming endpoint descriptor size before using baAssocJackID[], but the descriptor walker can still return a class-specific endpoint descriptor whose bLength exceeds the remaining bytes in the endpoint-extra scan. That leaves later flexible-array reads bounded by bLength, but not by the remaining bytes in the endpoint-extra scan. Stop walking when bLength is zero or extends past the remaining endpoint-extra scan. Fixes: 5c6cd7021a05 ("ALSA: usb-audio: Fix case when USB MIDI interface has more than one extra endpoint descriptor") Cc: stable@vger.kernel.org Signed-off-by: Cássio Gabriel Link: https://patch.msgid.link/20260507-usb-midi-endpoint-scan-bounds-v1-1-329d7348160e@gmail.com Signed-off-by: Takashi Iwai --- sound/usb/midi.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/sound/usb/midi.c b/sound/usb/midi.c index 0a5b8941ebda..d87e3f357cf7 100644 --- a/sound/usb/midi.c +++ b/sound/usb/midi.c @@ -1951,15 +1951,17 @@ static struct usb_ms_endpoint_descriptor *find_usb_ms_endpoint_descriptor( 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 == UAC_MS_GENERAL) return ms_ep; - if (!extra[0]) - break; - extralen -= extra[0]; - extra += extra[0]; + extralen -= length; + extra += length; } return NULL; }