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authorEric Dumazet <edumazet@google.com>2015-11-12 08:43:18 -0800
committerDavid S. Miller <davem@davemloft.net>2015-11-15 18:36:38 -0500
commit00fd38d938db3f1ab1c486549afc450cb7e751b1 (patch)
tree484653a166b88da8777c900a01b2b8e0d5455147 /net/ipv6
parent5883d9c6d7e680bcdc7a8a9ed2509cd10dd98206 (diff)
downloadblackbird-op-linux-00fd38d938db3f1ab1c486549afc450cb7e751b1.tar.gz
blackbird-op-linux-00fd38d938db3f1ab1c486549afc450cb7e751b1.zip
tcp: ensure proper barriers in lockless contexts
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>
Diffstat (limited to 'net/ipv6')
-rw-r--r--net/ipv6/tcp_ipv6.c19
1 files changed, 15 insertions, 4 deletions
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 5baa8e754e41..c5429a636f1a 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1690,6 +1690,8 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
const struct tcp_sock *tp = tcp_sk(sp);
const struct inet_connection_sock *icsk = inet_csk(sp);
const struct fastopen_queue *fastopenq = &icsk->icsk_accept_queue.fastopenq;
+ int rx_queue;
+ int state;
dest = &sp->sk_v6_daddr;
src = &sp->sk_v6_rcv_saddr;
@@ -1710,6 +1712,15 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
timer_expires = jiffies;
}
+ state = sk_state_load(sp);
+ if (state == TCP_LISTEN)
+ rx_queue = sp->sk_ack_backlog;
+ else
+ /* Because we don't lock the socket,
+ * we might find a transient negative value.
+ */
+ rx_queue = max_t(int, tp->rcv_nxt - tp->copied_seq, 0);
+
seq_printf(seq,
"%4d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
"%02X %08X:%08X %02X:%08lX %08X %5u %8d %lu %d %pK %lu %lu %u %u %d\n",
@@ -1718,9 +1729,9 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
src->s6_addr32[2], src->s6_addr32[3], srcp,
dest->s6_addr32[0], dest->s6_addr32[1],
dest->s6_addr32[2], dest->s6_addr32[3], destp,
- sp->sk_state,
- tp->write_seq-tp->snd_una,
- (sp->sk_state == TCP_LISTEN) ? sp->sk_ack_backlog : (tp->rcv_nxt - tp->copied_seq),
+ state,
+ tp->write_seq - tp->snd_una,
+ rx_queue,
timer_active,
jiffies_delta_to_clock_t(timer_expires - jiffies),
icsk->icsk_retransmits,
@@ -1732,7 +1743,7 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
jiffies_to_clock_t(icsk->icsk_ack.ato),
(icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
tp->snd_cwnd,
- sp->sk_state == TCP_LISTEN ?
+ state == TCP_LISTEN ?
fastopenq->max_qlen :
(tcp_in_initial_slowstart(tp) ? -1 : tp->snd_ssthresh)
);
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