releases/5.10.50/can-j1939-j1939_sk_setsockopt-prevent-allocation-of-.patch

From 99871fef18073addaf56f522afb3d38810a351ee Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Sun, 20 Jun 2021 14:38:42 +0200
Subject: can: j1939: j1939_sk_setsockopt(): prevent allocation of j1939 filter
 for optlen == 0

From: Norbert Slusarek <nslusarek@gmx.net>

[ Upstream commit aaf473d0100f64abc88560e2bea905805bcf2a8e ]

If optval != NULL and optlen == 0 are specified for SO_J1939_FILTER in
j1939_sk_setsockopt(), memdup_sockptr() will return ZERO_PTR for 0
size allocation. The new filter will be mistakenly assigned ZERO_PTR.
This patch checks for optlen != 0 and filter will be assigned NULL in
case of optlen == 0.

Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Link: https://lore.kernel.org/r/20210620123842.117975-1-nslusarek@gmx.net
Signed-off-by: Norbert Slusarek <nslusarek@gmx.net>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/can/j1939/socket.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index fce8bc8afeb7..e1a399821238 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -676,7 +676,7 @@ static int j1939_sk_setsockopt(struct socket *sock, int level, int optname,
 
 	switch (optname) {
 	case SO_J1939_FILTER:
-		if (!sockptr_is_null(optval)) {
+		if (!sockptr_is_null(optval) && optlen != 0) {
 			struct j1939_filter *f;
 			int c;
 
-- 
2.30.2