Messages in this thread | | | Date | Sat, 2 Jun 2007 19:11:48 -0300 | From | "Arnaldo Carvalho de Melo" <> | Subject | Re: [PATCH] fix race in AF_UNIX |
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On 6/2/07, Miklos Szeredi <miklos@szeredi.hu> wrote: > From: Miklos Szeredi <mszeredi@suse.cz> > > A recv() on an AF_UNIX, SOCK_STREAM socket can race with a > send()+close() on the peer, causing recv() to return zero, even though > the sent data should be received. > > This happens if the send() and the close() is performed between > skb_dequeue() and checking sk->sk_shutdown in unix_stream_recvmsg(): > > process A skb_dequeue() returns NULL, there's no data in the socket queue > process B new data is inserted onto the queue by unix_stream_sendmsg() > process B sk->sk_shutdown is set to SHUTDOWN_MASK by unix_release_sock() > process A sk->sk_shutdown is checked, unix_release_sock() returns zero > > I'm surprised nobody noticed this, it's not hard to trigger. Maybe > it's just (un)luck with the timing. > > It's possible to work around this bug in userspace, by retrying the > recv() once in case of a zero return value. > > Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> > --- > > Index: linux-2.6.22-rc2/net/unix/af_unix.c > =================================================================== > --- linux-2.6.22-rc2.orig/net/unix/af_unix.c 2007-06-02 23:45:47.000000000 +0200 > +++ linux-2.6.22-rc2/net/unix/af_unix.c 2007-06-02 23:45:49.000000000 +0200 > @@ -1711,20 +1711,23 @@ static int unix_stream_recvmsg(struct ki > int chunk; > struct sk_buff *skb; > > + unix_state_rlock(sk);
this function doesn't exist anymore, see:
http://git.kernel.org/?p=linux/kernel/git/davem/net-2.6.git;a=commitdiff;h=e97b6936b03dd0a62991f361c048cca38ac00198
There is also another AF_UNIX patch, also related to a race.
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