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From:   Phong Tran <tranmanphong@gmail.com>
To:     tranmanphong@gmail.com
Cc:     andreyknvl@google.com, gregkh@linuxfoundation.org,
        hans.verkuil@cisco.com, keescook@chromium.org,
        linux-kernel-mentees@lists.linuxfoundation.org,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        linux-usb@vger.kernel.org, mchehab@kernel.org,
        skhan@linuxfoundation.org,
        syzbot+eaaaf38a95427be88f4b@syzkaller.appspotmail.com,
        syzkaller-bugs@googlegroups.com, glider@google.com
Subject: [PATCH V2] media: usb: technisat-usb2: fix buffer overflow
Date:   Wed,  3 Jul 2019 09:14:44 +0700
Message-Id: <20190703021444.19954-1-tranmanphong@gmail.com>
In-Reply-To: <20190702140211.28399-1-tranmanphong@gmail.com>
References: <20190702140211.28399-1-tranmanphong@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The buffer will be overflow in case of the while loop can not break.
Add the checking buffer condition in while loop for avoiding
overlooping index.

This issue was reported by syzbot

Reported-by: syzbot+eaaaf38a95427be88f4b@syzkaller.appspotmail.com

Tested-by:
https://groups.google.com/d/msg/syzkaller-bugs/CySBCKuUOOs/t3PvVheSAAAJ

Signed-off-by: Phong Tran <tranmanphong@gmail.com>
---
Change Log:
 * V2: add IR_MAX_BUFFER_INDEX and adjust the while loop condition as comments
---
 drivers/media/usb/dvb-usb/technisat-usb2.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/technisat-usb2.c b/drivers/media/usb/dvb-usb/technisat-usb2.c
index c659e18b358b..cdabff97c1ea 100644
--- a/drivers/media/usb/dvb-usb/technisat-usb2.c
+++ b/drivers/media/usb/dvb-usb/technisat-usb2.c
@@ -49,6 +49,7 @@ MODULE_PARM_DESC(disable_led_control,
 		"disable LED control of the device (default: 0 - LED control is active).");
 
 /* device private data */
+#define IR_MAX_BUFFER_INDEX	63
 struct technisat_usb2_state {
 	struct dvb_usb_device *dev;
 	struct delayed_work green_led_work;
@@ -56,7 +57,7 @@ struct technisat_usb2_state {
 
 	u16 last_scan_code;
 
-	u8 buf[64];
+	u8 buf[IR_MAX_BUFFER_INDEX + 1];
 };
 
 /* debug print helpers */
@@ -655,7 +656,7 @@ static int technisat_usb2_get_ir(struct dvb_usb_device *d)
 #endif
 
 	ev.pulse = 0;
-	while (1) {
+	while (b <= (buf + IR_MAX_BUFFER_INDEX)) {
 		ev.pulse = !ev.pulse;
 		ev.duration = (*b * FIRMWARE_CLOCK_DIVISOR * FIRMWARE_CLOCK_TICK) / 1000;
 		ir_raw_event_store(d->rc_dev, &ev);
-- 
2.11.0