Re: [PATCH net 1/5] net/smc: fix dangling sock under state SMC_APPFINCLOSEWAIT

D. Wythe
2023-10-12T02:47:16Z

On 10/12/23 4:31 AM, Wenjia Zhang wrote:
>
>
> On 11.10.23 09:33, D. Wythe wrote:
>> From: "D. Wythe" <alibuda@linux.alibaba.com>
>>
>> Considering scenario:
>>
>>                 smc_cdc_rx_handler_rwwi
>> __smc_release
>>                 sock_set_flag
>> smc_close_active()
>> sock_set_flag
>>
>> __set_bit(DEAD)            __set_bit(DONE)
>>
>> Dues to __set_bit is not atomic, the DEAD or DONE might be lost.
>> if the DEAD flag lost, the state SMC_CLOSED  will be never be reached
>> in smc_close_passive_work:
>>
>> if (sock_flag(sk, SOCK_DEAD) &&
>>     smc_close_sent_any_close(conn)) {
>>     sk->sk_state = SMC_CLOSED;
>> } else {
>>     /* just shutdown, but not yet closed locally */
>>     sk->sk_state = SMC_APPFINCLOSEWAIT;
>> }
>>
>> Replace sock_set_flags or __set_bit to set_bit will fix this problem.
>> Since set_bit is atomic.
>>
> I didn't really understand the scenario. What is
> smc_cdc_rx_handler_rwwi()? What does it do? Don't it get the lock
> during the runtime?
>

Hi Wenjia,

Sorry for that, It is not smc_cdc_rx_handler_rwwi() but
smc_cdc_rx_handler();

Following is a more specific description of the issues

lock_sock()
__smc_release

smc_cdc_rx_handler()
smc_cdc_msg_recv()
bh_lock_sock()
smc_cdc_msg_recv_action()
sock_set_flag(DONE) sock_set_flag(DEAD)
__set_bit __set_bit
bh_unlock_sock()
release_sock()

Note :  bh_lock_sock and lock_sock are not mutually exclusive.
They are actually used for different purposes and contexts.

>> Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
>> ---
>>   net/smc/af_smc.c    | 4 ++--
>>   net/smc/smc.h       | 5 +++++
>>   net/smc/smc_cdc.c   | 2 +-
>>   net/smc/smc_close.c | 2 +-
>>   4 files changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
>> index bacdd97..5ad2a9f 100644
>> --- a/net/smc/af_smc.c
>> +++ b/net/smc/af_smc.c
>> @@ -275,7 +275,7 @@ static int __smc_release(struct smc_sock *smc)
>>         if (!smc->use_fallback) {
>>           rc = smc_close_active(smc);
>> -        sock_set_flag(sk, SOCK_DEAD);
>> +        smc_sock_set_flag(sk, SOCK_DEAD);
>>           sk->sk_shutdown |= SHUTDOWN_MASK;
>>       } else {
>>           if (sk->sk_state != SMC_CLOSED) {
>> @@ -1742,7 +1742,7 @@ static int smc_clcsock_accept(struct smc_sock
>> *lsmc, struct smc_sock **new_smc)
>>           if (new_clcsock)
>>               sock_release(new_clcsock);
>>           new_sk->sk_state = SMC_CLOSED;
>> -        sock_set_flag(new_sk, SOCK_DEAD);
>> +        smc_sock_set_flag(new_sk, SOCK_DEAD);
>>           sock_put(new_sk); /* final */
>>           *new_smc = NULL;
>>           goto out;
>> diff --git a/net/smc/smc.h b/net/smc/smc.h
>> index 24745fd..e377980 100644
>> --- a/net/smc/smc.h
>> +++ b/net/smc/smc.h
>> @@ -377,4 +377,9 @@ void smc_fill_gid_list(struct smc_link_group *lgr,
>>   int smc_nl_enable_hs_limitation(struct sk_buff *skb, struct
>> genl_info *info);
>>   int smc_nl_disable_hs_limitation(struct sk_buff *skb, struct
>> genl_info *info);
>>   +static inline void smc_sock_set_flag(struct sock *sk, enum
>> sock_flags flag)
>> +{
>> +    set_bit(flag, &sk->sk_flags);
>> +}
>> +
>>   #endif    /* __SMC_H */
>> diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
>> index 89105e9..01bdb79 100644
>> --- a/net/smc/smc_cdc.c
>> +++ b/net/smc/smc_cdc.c
>> @@ -385,7 +385,7 @@ static void smc_cdc_msg_recv_action(struct
>> smc_sock *smc,
>>           smc->sk.sk_shutdown |= RCV_SHUTDOWN;
>>           if (smc->clcsock && smc->clcsock->sk)
>>               smc->clcsock->sk->sk_shutdown |= RCV_SHUTDOWN;
>> -        sock_set_flag(&smc->sk, SOCK_DONE);
>> +        smc_sock_set_flag(&smc->sk, SOCK_DONE);
>>           sock_hold(&smc->sk); /* sock_put in close_work */
>>           if (!queue_work(smc_close_wq, &conn->close_work))
>>               sock_put(&smc->sk);
>> diff --git a/net/smc/smc_close.c b/net/smc/smc_close.c
>> index dbdf03e..449ef45 100644
>> --- a/net/smc/smc_close.c
>> +++ b/net/smc/smc_close.c
>> @@ -173,7 +173,7 @@ void smc_close_active_abort(struct smc_sock *smc)
>>           break;
>>       }
>>   -    sock_set_flag(sk, SOCK_DEAD);
>> +    smc_sock_set_flag(sk, SOCK_DEAD);
>>       sk->sk_state_change(sk);
>>         if (release_clcsock) {