[PATCH net] net/smc: fix panic smc_tcp_syn_recv_sock() while closing listen socket

D. Wythe
2023-09-20T12:08:59Z

From: "D. Wythe" <alibuda@linux.alibaba.com>

Consider the following scenarios:

smc_release
smc_close_active
write_lock_bh(&smc->clcsock->sk->sk_callback_lock);
smc->clcsock->sk->sk_user_data = NULL;
write_unlock_bh(&smc->clcsock->sk->sk_callback_lock);

smc_tcp_syn_recv_sock
smc = smc_clcsock_user_data(sk);
/* now */
/* smc == NULL */

Hence, we may read the a NULL value in smc_tcp_syn_recv_sock(). And
since we only unset sk_user_data during smc_release, it's safe to
drop the incoming tcp reqsock.

Fixes: ("net/smc: net/smc: Limit backlog connections"
Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
net/smc/af_smc.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index bacdd97..b4acf47 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -125,6 +125,8 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
struct sock *child;

smc = smc_clcsock_user_data(sk);
+ if (unlikely(!smc))
+ goto drop;

if (READ_ONCE(sk->sk_ack_backlog) + atomic_read(&smc->queued_smc_hs) >
sk->sk_max_ack_backlog)
--
1.8.3.1