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    SubjectRe: [PATCH] fix race in AF_UNIX
    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.

    - Arnaldo
    -
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