netdev - [PATCH net 2/2] can: isotp: convert struct tpcon::{idx,len} to unsigned int

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Message-Id: <20220105205443.1274709-3-mkl@pengutronix.de>
Date:   Wed,  5 Jan 2022 21:54:43 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, linux-can@...r.kernel.org,
        kernel@...gutronix.de, Marc Kleine-Budde <mkl@...gutronix.de>,
        stable@...r.kernel.org, Oliver Hartkopp <socketcan@...tkopp.net>,
        syzbot+4c63f36709a642f801c5@...kaller.appspotmail.com
Subject: [PATCH net 2/2] can: isotp: convert struct tpcon::{idx,len} to unsigned int

In isotp_rcv_ff() 32 bit of data received over the network is assigned
to struct tpcon::len. Later in that function the length is checked for
the maximal supported length against MAX_MSG_LENGTH.

As struct tpcon::len is an "int" this check does not work, if the
provided length overflows the "int".

Later on struct tpcon::idx is compared against struct tpcon::len.

To fix this problem this patch converts both struct tpcon::{idx,len}
to unsigned int.

Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol")
Link: https://lore.kernel.org/all/20220105132429.1170627-1-mkl@pengutronix.de
Cc: stable@...r.kernel.org
Acked-by: Oliver Hartkopp <socketcan@...tkopp.net>
Reported-by: syzbot+4c63f36709a642f801c5@...kaller.appspotmail.com
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 net/can/isotp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/can/isotp.c b/net/can/isotp.c
index df6968b28bf4..02cbcb2ecf0d 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -119,8 +119,8 @@ enum {
 };
 
 struct tpcon {
-	int idx;
-	int len;
+	unsigned int idx;
+	unsigned int len;
 	u32 state;
 	u8 bs;
 	u8 sn;
-- 
2.34.1