problem in tcp_v4_synq_add ?

Viorel Canja, Softwin
2004-03-09T11:27:50Z

Hello all,

I was looking through the networking code in 2.6.1 kernel and it seems
to me there could be a problem in tcp_ipv4.c in function tcp_v4_synq_add :

904 static void tcp_v4_synq_add(struct sock *sk, struct open_request *req)
905 {
906 struct tcp_opt *tp = tcp_sk(sk);
907 struct tcp_listen_opt *lopt = tp->listen_opt;
908 u32 h = tcp_v4_synq_hash(req->af.v4_req.rmt_addr, req->rmt_port, lopt->hash_rnd);
909
910 req->expires = jiffies + TCP_TIMEOUT_INIT;
911 req->retrans = 0;
912 req->sk = NULL;
913 req->dl_next = lopt->syn_table[h];
914
915 write_lock(&tp->syn_wait_lock);
916 lopt->syn_table[h] = req;
917 write_unlock(&tp->syn_wait_lock);
918
919 tcp_synq_added(sk);
920 }

Shouldn't "write_lock(&tp->syn_wait_lock);" be moved before
"req->dl_next = lopt->syn_table[h];" to avoid a race condition ?

I am new to the linux kernel so it is likely that I am missing
something. What am I missing ?

Thanks in advance,
Viorel