From: Baul Lee Date: Sun, 26 Jul 2026 06:50:20 +0000 (+0900) Subject: ALSA: usb-audio: fix stack info leak in RME Digiface status X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=441aaad150c57edaf57ee482a79a3bf4c5b7e353;p=thirdparty%2Flinux.git ALSA: usb-audio: fix stack info leak in RME Digiface status snd_rme_digiface_read_status() reads a four-word status block from the device into an uninitialised on-stack __le32 buf[4] and, whenever the vendor control-IN transfer does not return a negative error, copies all four words into the caller's status[]. snd_usb_ctl_msg() copies the full requested size back into the caller's buffer regardless of how many bytes the data stage actually delivered: buf = kmemdup(data, size, GFP_KERNEL); err = usb_control_msg(dev, pipe, request, requesttype, value, index, buf, size, timeout); memcpy(data, buf, size); usb_control_msg() returns the transferred length on a short control-IN, which is a non-negative value, and writes only that many bytes. The remainder of the copy back is the kmemdup()ed image of the caller's buffer, so a device answering with a short data stage leaves the trailing words of buf[] holding leftover kernel stack. The only guard in the caller is err < 0, so those words are stored into status[]. They then reach user space: snd_rme_digiface_get_status_val() selects a 16-bit halfword of status[] per the control's reg/mask, and the eight Digiface status controls together expose the whole 16-byte frame to an unprivileged reader of /dev/snd/controlC*. Zero-initialise the buffer so a short read yields zeros instead of stack residue. This mirrors snd_rme_get_status1(), which already clears its output word before the same kind of vendor read. Discovered by XBOW, triaged by Baul Lee Fixes: 611a96f6acf2 ("ALSA: usb-audio: Add mixer quirk for RME Digiface USB") Reported-by: Federico Kirschbaum Reported-by: Baul Lee Cc: stable@vger.kernel.org Signed-off-by: Baul Lee Link: https://patch.msgid.link/20260726065020.46070-1-baul.lee@xbow.com Signed-off-by: Takashi Iwai --- diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c index 10792d26fa94..74d26fd86efb 100644 --- a/sound/usb/mixer_quirks.c +++ b/sound/usb/mixer_quirks.c @@ -3496,7 +3496,7 @@ static int snd_rme_digiface_read_status(struct snd_kcontrol *kcontrol, u32 statu struct usb_mixer_elem_list *list = snd_kcontrol_chip(kcontrol); struct snd_usb_audio *chip = list->mixer->chip; struct usb_device *dev = chip->dev; - __le32 buf[4]; + __le32 buf[4] = {}; int err; err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0),