Re: KASAN: slab-out-of-bounds Read in garmin_read_process

[Oliver Neukum]

Am Samstag, den 21.03.2020, 06:40 -0700 schrieb syzbot:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    e17994d1 usb: core: kcov: collect coverage from usb comple..
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=16255ce5e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5d64370c438bc60
> dashboard link: https://syzkaller.appspot.com/bug?extid=d29e9263e13ce0b9f4fd
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1376a3f9e00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14c65fe3e00000

#syz test: https://github.com/google/kasan.git e17994d1
From 36ba9c64253cc4238376b74235a163288af59638 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@xxxxxxxx>
Date: Tue, 24 Mar 2020 13:46:31 +0100
Subject: [PATCH 2/2] garmin_gps: add sanity checking for data length

We must not process packets shorter than a packet ID

Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
---
 drivers/usb/serial/garmin_gps.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/serial/garmin_gps.c b/drivers/usb/serial/garmin_gps.c
index ffd984142171..a72fbbc65436 100644
--- a/drivers/usb/serial/garmin_gps.c
+++ b/drivers/usb/serial/garmin_gps.c
@@ -1138,8 +1138,8 @@ static void garmin_read_process(struct garmin_data *garmin_data_p,
 		   send it directly to the tty port */
 		if (garmin_data_p->flags & FLAGS_QUEUING) {
 			pkt_add(garmin_data_p, data, data_length);
-		} else if (bulk_data ||
-			   getLayerId(data) == GARMIN_LAYERID_APPL) {
+		} else if (bulk_data || (data_length >= sizeof(u32) &&
+			   getLayerId(data) == GARMIN_LAYERID_APPL)) {
 
 			spin_lock_irqsave(&garmin_data_p->lock, flags);
 			garmin_data_p->flags |= APP_RESP_SEEN;
-- 
2.16.4