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| author | Marouane El Moufid <eun0us@espilon.net> | 2026-08-23 13:55:48 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-09-02 14:26:44 +0200 |
| commit | 558fc4485ecc704edfe7876d6cebae4738ff7ef8 (patch) | |
| tree | 1ab234fbfef17855a44cc53cf3b1a8ca94b4df4f | |
| parent | 03a1bed450518af71d693e30842560b4b1cbb8aa (diff) | |
| download | linux-stable-558fc4485ecc704edfe7876d6cebae4738ff7ef8.tar.gz linux-stable-558fc4485ecc704edfe7876d6cebae4738ff7ef8.zip | |
ALSA: usb-audio: fix OOB write in snd_usbmidi_novation_output()
commit 1035a8f63bae28e498b0e7b5ac91d749844a7158 upstream.
snd_usbmidi_novation_output() lays out a two-byte header at
transfer_buffer[0..1] and passes &transfer_buffer[2] together with a
length of ep->max_transfer - 2 to snd_rawmidi_transmit():
count = snd_rawmidi_transmit(ep->ports[0].substream,
&transfer_buffer[2],
ep->max_transfer - 2);
ep->max_transfer comes from the output endpoint's wMaxPacketSize via
usb_maxpacket(). A malformed or malicious device can advertise a bulk
OUT endpoint with a wMaxPacketSize of 1 - the USB core only clamps this
value downwards - so ep->max_transfer becomes 1 and the count argument
becomes -1.
snd_rawmidi_transmit() passes the negative count on to
__snd_rawmidi_transmit_peek(), where "if (count1 > count) count1 = count"
leaves count1 negative; get_aligned_size() keeps it negative for a
byte-stream substream, so the following memcpy(buffer, ..., count1) runs
with a (size_t)-1 length and writes far past the transfer buffer, which
was allocated with usb_alloc_coherent(ep->max_transfer).
This is the same class of bug that was fixed for snd_usbmidi_akai_output()
in commit 0970274613fb ("ALSA: usb-audio: fix OOB write in
snd_usbmidi_akai_output()"); the novation output routine was left
unguarded. Bail out when the endpoint cannot hold the two-byte header
plus at least one payload byte.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Marouane El Moufid <eun0us@espilon.net>
Link: https://patch.msgid.link/178749334830.543645.13722252148340572274@espilon.net
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | sound/usb/midi.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/sound/usb/midi.c b/sound/usb/midi.c index 6b491bfe852b..1f2267e9d5ed 100644 --- a/sound/usb/midi.c +++ b/sound/usb/midi.c @@ -894,6 +894,8 @@ static void snd_usbmidi_novation_output(struct snd_usb_midi_out_endpoint *ep, if (!ep->ports[0].active) return; + if (ep->max_transfer < 3) + return; transfer_buffer = urb->transfer_buffer; count = snd_rawmidi_transmit(ep->ports[0].substream, &transfer_buffer[2], |