[PATCH 5.10 17/25] can: isotp: convert struct tpcon::{idx,len} to unsigned int

[Greg Kroah-Hartman]

From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>

commit 5f33a09e769a9da0482f20a6770a342842443776 upstream.

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@xxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Acked-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
Reported-by: syzbot+4c63f36709a642f801c5@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/can/isotp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- 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;