[PATCH 5.17 398/772] sctp: read sk->sk_bound_dev_if once in sctp_rcv()

Greg Kroah-Hartman
2022-06-07T21:11:50Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit a20ea298071f46effa3aaf965bf9bb34c901db3f ]

sctp_rcv() reads sk->sk_bound_dev_if twice while the socket
is not locked. Another cpu could change this field under us.

Fixes: 0fd9a65a76e8 ("[SCTP] Support SO_BINDTODEVICE socket option on incoming packets.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sctp/input.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 90e12bafdd48..4f43afa8678f 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -92,6 +92,7 @@ int sctp_rcv(struct sk_buff *skb)
struct sctp_chunk *chunk;
union sctp_addr src;
union sctp_addr dest;
+ int bound_dev_if;
int family;
struct sctp_af *af;
struct net *net = dev_net(skb->dev);
@@ -169,7 +170,8 @@ int sctp_rcv(struct sk_buff *skb)
* If a frame arrives on an interface and the receiving socket is
* bound to another interface, via SO_BINDTODEVICE, treat it as OOTB
*/
- if (sk->sk_bound_dev_if && (sk->sk_bound_dev_if != af->skb_iif(skb))) {
+ bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
+ if (bound_dev_if && (bound_dev_if != af->skb_iif(skb))) {
if (transport) {
sctp_transport_put(transport);
asoc = NULL;
--
2.35.1