This is a note to let you know that I've just added the patch titled
tcp: Fix race in tcp_poll
to the 2.6.27-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp-fix-race-in-tcp_poll.patch
and it can be found in the queue-2.6.27 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 7938b8515a9ed0a49b160b4c95ef3ed8bccbeb11 Mon Sep 17 00:00:00 2001
From: Tom Marshall <[email protected]>
Date: Mon, 20 Sep 2010 15:42:05 -0700
Subject: tcp: Fix race in tcp_poll
From: Tom Marshall <[email protected]>
[ Upstream commit a4d258036ed9b2a1811c3670c6099203a0f284a0 ]
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 <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
net/ipv4/tcp.c | 7 +++++--
net/ipv4/tcp_input.c | 2 ++
2 files changed, 7 insertions(+), 2 deletions(-)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -347,8 +347,6 @@ unsigned int tcp_poll(struct file *file,
*/
mask = 0;
- if (sk->sk_err)
- mask = POLLERR;
/*
* POLLHUP is certainly not done right. But poll() doesn't
@@ -413,6 +411,11 @@ unsigned int tcp_poll(struct file *file,
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;
}
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3617,6 +3617,8 @@ 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);
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.27/tcp-fix-race-in-tcp_poll.patch
_______________________________________________
stable mailing list
[email protected]
http://linux.kernel.org/mailman/listinfo/stable
