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tcp: ensure proper barriers in lockless contexts

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Some functions access TCP sockets without holding a lock and
might output non consistent data, depending on compiler and or
architecture.

tcp_diag_get_info(), tcp_get_info(), tcp_poll(), get_tcp4_sock() ...

Introduce sk_state_load() and sk_state_store() to fix the issues,
and more clearly document where this lack of locking is happening.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-11-12 08:43:18 -08:00 • committed by David S. Miller
parent 5883d9c6d7
commit 00fd38d938
6 changed files with 62 additions and 23 deletions
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4
net/ipv4/inet_connection_sock.c
View file

@ -563,7 +563,7 @@ static void reqsk_timer_handler(unsigned long data)
int max_retries, thresh;
u8 defer_accept;
if (sk_listener->sk_state != TCP_LISTEN)
if (sk_state_load(sk_listener) != TCP_LISTEN)
goto drop;
max_retries = icsk->icsk_syn_retries ? : sysctl_tcp_synack_retries;
@ -749,7 +749,7 @@ int inet_csk_listen_start(struct sock *sk, int backlog)
* It is OK, because this socket enters to hash table only
* after validation is complete.
*/
sk->sk_state = TCP_LISTEN;
sk_state_store(sk, TCP_LISTEN);
if (!sk->sk_prot->get_port(sk, inet->inet_num)) {
inet->inet_sport = htons(inet->inet_num);