This is a note to let you know that I've just added the patch titled
unix: fix a race condition in unix_release()
to the 3.4-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:
unix-fix-a-race-condition-in-unix_release.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From fe05c83620e4b667c0f12d6d2cc2882b84d53376 Mon Sep 17 00:00:00 2001
From: Paul Moore <pmoore@xxxxxxxxxx>
Date: Mon, 25 Mar 2013 03:18:33 +0000
Subject: unix: fix a race condition in unix_release()
From: Paul Moore <pmoore@xxxxxxxxxx>
[ Upstream commit ded34e0fe8fe8c2d595bfa30626654e4b87621e0 ]
As reported by Jan, and others over the past few years, there is a
race condition caused by unix_release setting the sock->sk pointer
to NULL before properly marking the socket as dead/orphaned. This
can cause a problem with the LSM hook security_unix_may_send() if
there is another socket attempting to write to this partially
released socket in between when sock->sk is set to NULL and it is
marked as dead/orphaned. This patch fixes this by only setting
sock->sk to NULL after the socket has been marked as dead; I also
take the opportunity to make unix_release_sock() a void function
as it only ever returned 0/success.
Dave, I think this one should go on the -stable pile.
Special thanks to Jan for coming up with a reproducer for this
problem.
Reported-by: Jan Stancek <jan.stancek@xxxxxxxxx>
Signed-off-by: Paul Moore <pmoore@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/unix/af_unix.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -374,7 +374,7 @@ static void unix_sock_destructor(struct
#endif
}
-static int unix_release_sock(struct sock *sk, int embrion)
+static void unix_release_sock(struct sock *sk, int embrion)
{
struct unix_sock *u = unix_sk(sk);
struct path path;
@@ -443,8 +443,6 @@ static int unix_release_sock(struct sock
if (unix_tot_inflight)
unix_gc(); /* Garbage collect fds */
-
- return 0;
}
static void init_peercred(struct sock *sk)
@@ -694,9 +692,10 @@ static int unix_release(struct socket *s
if (!sk)
return 0;
+ unix_release_sock(sk, 0);
sock->sk = NULL;
- return unix_release_sock(sk, 0);
+ return 0;
}
static int unix_autobind(struct socket *sock)
Patches currently in stable-queue which might be from pmoore@xxxxxxxxxx are
queue-3.4/unix-fix-a-race-condition-in-unix_release.patch
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