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Date: Sat, 4 Nov 2006 22:06:41 +0100 From: Willy Tarreau <w@....eu> To: NeilBrown <neilb@...e.de> Cc: linux-kernel@...r.kernel.org Subject: Re: [PATCH 30/61] knfsd: Fix race that can disable NFS server. Hi Neil, I don't know if you noticed my request for ACK as I did not get any response. I think that your patch here is a good candidate for 2.4 too, I would just like to get your confirmation before merging it. Thanks in advance, willy On Wed, Nov 01, 2006 at 08:11:11AM +0100, Willy Tarreau wrote: On Tue, Oct 31, 2006 at 09:34:10PM -0800, Chris Wright wrote: > -stable review patch. If anyone has any objections, please let us know. > ------------------ > > From: NeilBrown <neilb@...e.de> > > This is a long standing bug that seems to have only recently become > apparent, presumably due to increasing use of NFS over TCP - many > distros seem to be making it the default. > > The SK_CONN bit gets set when a listening socket may be ready > for an accept, just as SK_DATA is set when data may be available. > > It is entirely possible for svc_tcp_accept to be called with neither > of these set. It doesn't happen often but there is a small race in > svc_sock_enqueue as SK_CONN and SK_DATA are tested outside the > spin_lock. They could be cleared immediately after the test and > before the lock is gained. > > This normally shouldn't be a problem. The sockets are non-blocking so > trying to read() or accept() when ther is nothing to do is not a problem. > > However: svc_tcp_recvfrom makes the decision "Should I accept() or > should I read()" based on whether SK_CONN is set or not. This usually > works but is not safe. The decision should be based on whether it is > a TCP_LISTEN socket or a TCP_CONNECTED socket. > > > Signed-off-by: Neil Brown <neilb@...e.de> > Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de> > Signed-off-by: Chris Wright <chrisw@...s-sol.org> > > --- > net/sunrpc/svcsock.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- linux-2.6.18.1.orig/net/sunrpc/svcsock.c > +++ linux-2.6.18.1/net/sunrpc/svcsock.c > @@ -902,7 +902,7 @@ svc_tcp_recvfrom(struct svc_rqst *rqstp) > return 0; > } > > - if (test_bit(SK_CONN, &svsk->sk_flags)) { > + if (svsk->sk_sk->sk_state == TCP_LISTEN) { > svc_tcp_accept(svsk); > svc_sock_received(svsk); > return 0; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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