[PATCH 09/11] ALSA: line6: Reject too small max packet sizes

[Takashi Iwai <tiwai@suse.de>]

Although the LINE6 driver has a sanity check for the given max packet
sizes, it still has an implicit requirement of the minimal size being
bytes-per-frame; e.g. the impulse test signal assuming the fixed size,
and when a too small size is specified by a malformed USB descriptor,
this may lead to an OOB access.

Change the sanity check conditions to reject too small max packet
sizes for avoiding the scenario above.

Fixes: 3450121997ce ("ALSA: line6: Fix write on zero-sized buffer")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/usb/line6/pcm.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sound/usb/line6/pcm.c b/sound/usb/line6/pcm.c
index 2932eaf157f4..998869dc4613 100644
--- a/sound/usb/line6/pcm.c
+++ b/sound/usb/line6/pcm.c
@@ -554,7 +554,11 @@ int line6_init_pcm(struct usb_line6 *line6,
 	line6pcm->max_packet_size_out =
 		usb_maxpacket(line6->usbdev,
 			usb_sndisocpipe(line6->usbdev, ep_write));
-	if (!line6pcm->max_packet_size_in || !line6pcm->max_packet_size_out) {
+	/* reject max packet sizes smaller than bytes-per-frame;
+	 * (the magic number 6 is taken from the playback case)
+	 */
+	if (line6pcm->max_packet_size_in < 6 ||
+	    line6pcm->max_packet_size_out < 6) {
 		dev_err(line6pcm->line6->ifcdev,
 			"cannot get proper max packet size\n");
 		return -EINVAL;
-- 
2.55.0