netdev - [net 1/2] can: j1939: j1939_sk_setsockopt(): prevent allocation of j1939 filter for optlen == 0

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Date:   Thu, 24 Jun 2021 08:41:59 +0200
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, Norbert Slusarek <nslusarek@....net>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [net 1/2] can: j1939: j1939_sk_setsockopt(): prevent allocation of j1939 filter for optlen == 0

From: Norbert Slusarek <nslusarek@....net>

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@....net>
Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 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;
 

base-commit: c2f5c57d99debf471a1b263cdf227e55f1364e95
-- 
2.30.2