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authorTom Marshall <tdm.code@gmail.com>2010-09-20 15:42:05 -0700
committerDavid S. Miller <davem@davemloft.net>2010-09-20 15:42:05 -0700
commita4d258036ed9b2a1811c3670c6099203a0f284a0 (patch)
tree58412022664aef745a99d254d20cf1a66aabda44 /net
parent9828e6e6e3f19efcb476c567b9999891d051f52f (diff)
tcp: Fix race in tcp_poll
If a RST comes in immediately after checking sk->sk_err, tcp_poll will return POLLIN but not POLLOUT. Fix this by checking sk->sk_err at the end of tcp_poll. Additionally, ensure the correct order of operations on SMP machines with memory barriers. Signed-off-by: Tom Marshall <tdm.code@gmail.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp.c7
-rw-r--r--net/ipv4/tcp_input.c2
2 files changed, 7 insertions, 2 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 3fb1428e526e..95d75d443927 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -386,8 +386,6 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
*/
mask = 0;
- if (sk->sk_err)
- mask = POLLERR;
/*
* POLLHUP is certainly not done right. But poll() doesn't
@@ -457,6 +455,11 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
if (tp->urg_data & TCP_URG_VALID)
mask |= POLLPRI;
}
+ /* This barrier is coupled with smp_wmb() in tcp_reset() */
+ smp_rmb();
+ if (sk->sk_err)
+ mask |= POLLERR;
+
return mask;
}
EXPORT_SYMBOL(tcp_poll);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e663b78a2ef6..149e79ac2891 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4048,6 +4048,8 @@ static void tcp_reset(struct sock *sk)
default:
sk->sk_err = ECONNRESET;
}
+ /* This barrier is coupled with smp_rmb() in tcp_poll() */
+ smp_wmb();
if (!sock_flag(sk, SOCK_DEAD))
sk->sk_error_report(sk);

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