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b=vbIlXA3/n1ya8GmBkf//b0+ctxmtiML1N3CmfKhk6kARslIq/99j6ZCxRmqvHq0iOqmw4E mZDZT7usDfaxmJAQ== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id DA2343EA63; Sat, 13 Dec 2025 09:31:34 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id iNylM3YyPWmHJwAAD6G6ig (envelope-from ); Sat, 13 Dec 2025 09:31:34 +0000 Date: Sat, 13 Dec 2025 10:31:34 +0100 Message-ID: <87tsxu918p.wl-tiwai@suse.de> From: Takashi Iwai To: "Vulnerability Report" Cc: "Jaroslav Kysela" , "Takashi Iwai" , "alsa-devel" , "linux-kernel" Subject: Re: [PATCH] ALSA: usb-mixer: us16x08: validate meter packet indices In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/30.1 Mule/6.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-3.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-0.998]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_FIVE(0.00)[5]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:mid]; TO_DN_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spam-Level: X-Rspamd-Queue-Id: 1A81A5BD78 X-Spam-Flag: NO X-Spam-Score: -3.51 On Fri, 12 Dec 2025 07:54:37 +0100, Vulnerability Report wrote: > > Hi, > > while fuzzing a USB gadget that emulates a Tascam US-16x08 we found that > get_meter_levels_from_urb() in mixer_us16x08.c uses a channel index > taken directly from the 64-byte meter packet to index meter_level[], > comp_level[] and master_level[] without any bounds checking. A malformed > packet can therefore cause out-of-bounds writes in the > snd_us16x08_meter_store. > > > A malicious USB audio device (or USB gadget implementation) that > pretends to be a US-16x08-compatible interface can trigger this by > sending crafted meter packets. We have a small USB gadget-based PoC for > this behaviour and can share it if that would be helpful. > > > This driver is used by common distributions (e.g. Ubuntu) when a > US-16x08 or compatible USB audio device is present. The same pattern is > present in current mainline kernels. > > > This issue was first reported via security@kernel.org. The kernel > security team explained that, in the upstream threat model, USB > endpoints are expected to be trusted (i.e. only trusted devices should > be bound to drivers), so they consider this a normal bug rather than a > security vulnerability, and asked us to send a fix to the development > lists. The patch below adds simple range checks before updating these > arrays. > > > Suggested patch: > > > --- >  sound/usb/mixer_us16x08.c | 15 +++++++++++++-- >  1 file changed, 13 insertions(+), 2 deletions(-) > > > diff --git a/sound/usb/mixer_us16x08.c b/sound/usb/mixer_us16x08.c > index XXXXXXXX..YYYYYYYY 100644 > --- a/sound/usb/mixer_us16x08.c > +++ b/sound/usb/mixer_us16x08.c > @@ -647,15 +647,26 @@ static int snd_get_meter_comp_index(struct snd_us16x08_meter_store *store) >  /* retrieve the meter level values from URB message */ >  static void get_meter_levels_from_urb(int s, >       struct snd_us16x08_meter_store *store, >       u8 *meter_urb) >  { >       int val = MUC2(meter_urb, s) + (MUC3(meter_urb, s) << 8); > +     int ch = MUB2(meter_urb, s) - 1; > + > +     if (ch < 0) > +           return; >   >       if (MUA0(meter_urb, s) == 0x61 && MUA1(meter_urb, s) == 0x02 && > -           MUA2(meter_urb, s) == 0x04 && MUB0(meter_urb, s) == 0x62) { > -           if (MUC0(meter_urb, s) == 0x72) > -                 store->meter_level[MUB2(meter_urb, s) - 1] = val; > -           if (MUC0(meter_urb, s) == 0xb2) > -                 store->comp_level[MUB2(meter_urb, s) - 1] = val; > -     } > +           MUA2(meter_urb, s) == 0x04 && MUB0(meter_urb, s) == 0x62) { > +           if (ch < SND_US16X08_MAX_CHANNELS) { > +                 if (MUC0(meter_urb, s) == 0x72) > +                       store->meter_level[ch] = val; > +                 if (MUC0(meter_urb, s) == 0xb2) > +                       store->comp_level[ch] = val; > +           } > +     } >       if (MUA0(meter_urb, s) == 0x61 && MUA1(meter_urb, s) == 0x02 && > -           MUA2(meter_urb, s) == 0x02 && MUB0(meter_urb, s) == 0x62) > -           store->master_level[MUB2(meter_urb, s) - 1] = val; > +           MUA2(meter_urb, s) == 0x02 && MUB0(meter_urb, s) == 0x62) { > +           if (ch < ARRAY_SIZE(store->master_level)) > +                 store->master_level[ch] = val; > +     } >  } > > > Reported-by: DARKNAVY (@DarkNavyOrg) Signed-off-by: DARKNAVY (@DarkNavyOrg)