Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763028Ab3DCTB6 (ORCPT ); Wed, 3 Apr 2013 15:01:58 -0400 Received: from mail-vc0-f169.google.com ([209.85.220.169]:49299 "EHLO mail-vc0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760290Ab3DCTB5 (ORCPT ); Wed, 3 Apr 2013 15:01:57 -0400 MIME-Version: 1.0 In-Reply-To: <1365014637.13853.36.camel@edumazet-glaptop> References: <20130402221104.163133110@linuxfoundation.org> <20130402221116.307254752@linuxfoundation.org> <87vc833kpf.fsf@turtle.gmx.de> <1364997630.13853.19.camel@edumazet-glaptop> <87a9pfzm33.fsf@turtle.gmx.de> <1365003300.13853.25.camel@edumazet-glaptop> <515C6DCD.50902@mit.edu> <1365014637.13853.36.camel@edumazet-glaptop> From: Andy Lutomirski Date: Wed, 3 Apr 2013 12:01:36 -0700 Message-ID: Subject: Re: [ 105/124] af_unix: dont send SCM_CREDENTIAL when dest socket is NULL To: Eric Dumazet Cc: "Eric W. Biederman" , Sven Joachim , Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , stable@vger.kernel.org, Ding Tianhong , Eric Dumazet , "David S. Miller" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1824 Lines: 53 On Wed, Apr 3, 2013 at 11:43 AM, Eric Dumazet wrote: > On Wed, 2013-04-03 at 10:58 -0700, Andy Lutomirski wrote: > >> >> This sounds suspiciously like an SCM_CREDENTIALS bug triggered by a >> race. There's a fix (that needs both a new version from me and a review >> by someone) here: >> >> http://www.spinics.net/lists/netdev/msg229948.html > > Hmm... this is not a stable candidate, IMHO. Agreed. > > This has to be fixed (if needed) in a more easy way. > > What about this one liner ? > > CC Eric W. Biederman as he wrote commit > dbe9a4173ea53b72b2c3 > (scm: Don't use struct ucred in NETLINK_CB and struct scm_cookie.) > > diff --git a/include/net/scm.h b/include/net/scm.h > index 975cca0..42359d8 100644 > --- a/include/net/scm.h > +++ b/include/net/scm.h > @@ -120,7 +120,7 @@ static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg, > return; > } > > - if (test_bit(SOCK_PASSCRED, &sock->flags)) { > + if (test_bit(SOCK_PASSCRED, &sock->flags) && scm->creds.pid) { > struct user_namespace *current_ns = current_user_ns(); > struct ucred ucreds = { > .pid = scm->creds.pid, > > That looks like it's correct. If it gets applied, I'll respin my patches on top of it. (This approach may be a POSIX violation for all I know, and it's even possible that some really fragile userspace breaks. But I doubt it, and anything that will break as a result is already operating in a highly confused state; hence the original problem.) --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/