[PATCH] net/smc: loop in smc_listen

[PATCH] net/smc: loop in smc_listen

[Daxing Guo]

From: Guo DaXing <guodaxing@huawei.com>

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 <guodaxing@huawei.com>
---
 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

Re: [PATCH] net/smc: loop in smc_listen

[Tony Lu]

On Sat, Nov 20, 2021 at 03:54:51PM +0800, Daxing Guo wrote:
> From: Guo DaXing <guodaxing@huawei.com>
> 
> 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

> 
> Signed-off-by: Guo DaXing <guodaxing@huawei.com>
> ---
>  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

Re: [PATCH] net/smc: loop in smc_listen

[Karsten Graul]

On 20/11/2021 08:54, Daxing Guo wrote:
> From: Guo DaXing <guodaxing@huawei.com>
> 
> 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 <guodaxing@huawei.com>
> ---

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

Re: [PATCH] net/smc: loop in smc_listen

[Tony Lu]

On Sat, Nov 20, 2021 at 03:54:51PM +0800, Daxing Guo wrote:
> From: Guo DaXing <guodaxing@huawei.com>
> 
> 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 <guodaxing@huawei.com>

It works in my testing environment, thanks.

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

Re: [PATCH] net/smc: loop in smc_listen

[greg]

On Fri, Nov 19, 2021 at 03:21:16AM +0000, guodaxing wrote:
> The kernel_listen function in smc_listen will fail when all the available

<snip>

You need to resend this without html, as the mailing list rejects html
patches and we can not apply them.

thanks,

greg k-h