linux-kernel - [PATCH 5.12 476/700] can: j1939: j1939_sk_setsockopt(): prevent allocation of j1939 filter for optlen == 0

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Message-Id: <20210712061027.228023799@linuxfoundation.org>
Date:   Mon, 12 Jul 2021 08:09:19 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Norbert Slusarek <nslusarek@....net>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 476/700] can: j1939: j1939_sk_setsockopt(): prevent allocation of j1939 filter for optlen == 0

From: Norbert Slusarek <nslusarek@....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@....net>
Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Sasha Levin <sashal@...nel.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