| From 35d06714991983a6586aaf6ed453b73dc54a39ec Mon Sep 17 00:00:00 2001 |
| From: Tom Marshall <tdm.code@gmail.com> |
| Date: Mon, 20 Sep 2010 15:42:05 -0700 |
| Subject: [PATCH] tcp: Fix race in tcp_poll |
| |
| commit a4d258036ed9b2a1811c3670c6099203a0f284a0 upstream. |
| |
| 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> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| --- |
| net/ipv4/tcp.c | 7 +++++-- |
| net/ipv4/tcp_input.c | 2 ++ |
| 2 files changed, 7 insertions(+), 2 deletions(-) |
| |
| diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c |
| index 1b40924..3fa16d9 100644 |
| --- a/net/ipv4/tcp.c |
| +++ b/net/ipv4/tcp.c |
| @@ -388,8 +388,6 @@ 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 |
| @@ -459,6 +457,11 @@ 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; |
| } |
| |
| diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c |
| index f240f57..dd0c9af 100644 |
| --- a/net/ipv4/tcp_input.c |
| +++ b/net/ipv4/tcp_input.c |
| @@ -4040,6 +4040,8 @@ 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); |
| -- |
| 1.7.0.4 |
| |