[PATCH] net/smc: loop in smc_listen

From: Guo DaXing <redacted>

The kernel_listen function in smc_listen will fail when all the available
ports are occupied.  At this point smc->clcsock->sk->sk_data_ready has 
been changed to smc_clcsock_data_ready.  When we call smc_listen again, 
now both smc->clcsock->sk->sk_data_ready and smc->clcsk_data_ready point 
to the smc_clcsock_data_ready function.

The smc_clcsock_data_ready() function calls lsmc->clcsk_data_ready which 
now points to itself resulting in an infinite loop.

This patch restores smc->clcsock->sk->sk_data_ready with the old value.

Signed-off-by: Guo DaXing <redacted>
---
 net/smc/af_smc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 59284da9116d..078f5edf6d4d 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c

@@ -2120,8 +2120,10 @@ static int smc_listen(struct socket *sock, int backlog)
 	smc->clcsock->sk->sk_user_data =
 		(void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
 	rc = kernel_listen(smc->clcsock, backlog);
-	if (rc)
+	if (rc) {
+		smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready;
 		goto out;
+	}
 	sk->sk_max_ack_backlog = backlog;
 	sk->sk_ack_backlog = 0;
 	sk->sk_state = SMC_LISTEN;

-- 
2.20.1

On Sat, Nov 20, 2021 at 03:54:51PM +0800, Daxing Guo wrote:

From: Guo DaXing <redacted>

The kernel_listen function in smc_listen will fail when all the available
ports are occupied.  At this point smc->clcsock->sk->sk_data_ready has 
been changed to smc_clcsock_data_ready.  When we call smc_listen again, 
now both smc->clcsock->sk->sk_data_ready and smc->clcsk_data_ready point 
to the smc_clcsock_data_ready function.

The smc_clcsock_data_ready() function calls lsmc->clcsk_data_ready which 
now points to itself resulting in an infinite loop.

This patch restores smc->clcsock->sk->sk_data_ready with the old value.

Hi Guo,

This indeed seems to be an issue. When listen fails, the original
clcsock's sk_data_ready overwrites by smc_clcsock_data_ready and can't
be recovered. I will also test it in my environment, thanks.

Cheers,
Tony Lu

On 20/11/2021 08:54, Daxing Guo wrote:

From: Guo DaXing <redacted>

The kernel_listen function in smc_listen will fail when all the available
ports are occupied.  At this point smc->clcsock->sk->sk_data_ready has 
been changed to smc_clcsock_data_ready.  When we call smc_listen again, 
now both smc->clcsock->sk->sk_data_ready and smc->clcsk_data_ready point 
to the smc_clcsock_data_ready function.

The smc_clcsock_data_ready() function calls lsmc->clcsk_data_ready which 
now points to itself resulting in an infinite loop.

This patch restores smc->clcsock->sk->sk_data_ready with the old value.

Signed-off-by: Guo DaXing <redacted>
---

Thanks for your patch, I will pick it up and submit it to the net tree.

On Sat, Nov 20, 2021 at 03:54:51PM +0800, Daxing Guo wrote:

From: Guo DaXing <redacted>

The kernel_listen function in smc_listen will fail when all the available
ports are occupied.  At this point smc->clcsock->sk->sk_data_ready has 
been changed to smc_clcsock_data_ready.  When we call smc_listen again, 
now both smc->clcsock->sk->sk_data_ready and smc->clcsk_data_ready point 
to the smc_clcsock_data_ready function.

The smc_clcsock_data_ready() function calls lsmc->clcsk_data_ready which 
now points to itself resulting in an infinite loop.

This patch restores smc->clcsock->sk->sk_data_ready with the old value.

Signed-off-by: Guo DaXing <redacted>

It works in my testing environment, thanks.

Acked-by: Tony Lu <tonylu@linux.alibaba.com>