From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760110AbcKCSpI (ORCPT ); Thu, 3 Nov 2016 14:45:08 -0400 Received: from mail-ua0-f178.google.com ([209.85.217.178]:34323 "EHLO mail-ua0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757299AbcKCSpG (ORCPT ); Thu, 3 Nov 2016 14:45:06 -0400 MIME-Version: 1.0 In-Reply-To: <20161103183533.GH8514@localhost.localdomain> References: <20161019165754.GD2958@localhost.localdomain> <20161103175220.GG8514@localhost.localdomain> <20161103183533.GH8514@localhost.localdomain> From: Andrey Konovalov Date: Thu, 3 Nov 2016 19:45:04 +0100 Message-ID: Subject: Re: net/sctp: use-after-free in __sctp_connect To: Marcelo Ricardo Leitner Cc: Vlad Yasevich , Neil Horman , "David S. Miller" , linux-sctp@vger.kernel.org, netdev , LKML , syzkaller , Kostya Serebryany , Alexander Potapenko , Eric Dumazet , Dmitry Vyukov Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 3, 2016 at 7:35 PM, Marcelo Ricardo Leitner wrote: > On Thu, Nov 03, 2016 at 07:02:47PM +0100, Andrey Konovalov wrote: >> On Thu, Nov 3, 2016 at 6:52 PM, Marcelo Ricardo Leitner >> wrote: >> > On Thu, Nov 03, 2016 at 06:11:01PM +0100, Andrey Konovalov wrote: >> >> On Wed, Nov 2, 2016 at 11:42 PM, Andrey Konovalov wrote: >> >> > On Wed, Oct 19, 2016 at 6:57 PM, Marcelo Ricardo Leitner >> >> > wrote: >> >> >> On Wed, Oct 19, 2016 at 02:25:24PM +0200, Andrey Konovalov wrote: >> >> >>> Hi, >> >> >>> >> >> >>> I've got the following error report while running the syzkaller fuzzer: >> >> >>> >> >> >>> ================================================================== >> >> >>> BUG: KASAN: use-after-free in __sctp_connect+0xabe/0xbf0 at addr >> >> >>> ffff88006b1dc610 >> >> >> >> >> >> Seems this is the same that Dmitry Vyukov had reported back in Jan 13th. >> >> >> So far I couldn't identify the reason. >> >> >> "Good" to know it's still there, thanks for reporting it. >> >> >> >> Hi Marcelo, >> >> >> > >> > Hi >> > >> >> So I've looked at the code. >> >> As far as I understand, the problem is a race condition between >> >> setsockopt(SCTP_SOCKOPT_CONNECTX) and shutdown on an sctp socket. >> >> setsockopt() calls sctp_wait_for_connect(), which exits the for loop >> >> on the sk->sk_shutdown & RCV_SHUTDOWN if clause, and then frees asoc >> >> with sctp_association_put() and returns err = 0. >> >> Then __sctp_connect() checks that err == 0 and reads asoc->assoc_id >> >> from the freed asoc. >> > >> > Suddenly this seems familiar. Your description makes sense, thanks for >> > looking deeper into this, Andrey. >> > >> > This fix should do it, can you please try it? I'll post it properly >> > if it works. >> >> Yes, it fixes the issue. >> >> Tested-by: Andrey Konovalov >> >> Thanks for the fix! > > Ahm this other fix looks better: do the read before calling > sctp_wait_for_connect() as that id won't change in this call and the > application shouldn't trust this number if an error is returned, so > there should be no issues by returning it in such situation. > > Can you please confirm this one also works? Thanks! Sure! This one also works. Tested-by: Andrey Konovalov > > ---8<--- > > diff --git a/net/sctp/socket.c b/net/sctp/socket.c > index 6cdc61c21438..be1d9bb98230 100644 > --- a/net/sctp/socket.c > +++ b/net/sctp/socket.c > @@ -1214,9 +1214,12 @@ static int __sctp_connect(struct sock *sk, > > timeo = sock_sndtimeo(sk, f_flags & O_NONBLOCK); > > - err = sctp_wait_for_connect(asoc, &timeo); > - if ((err == 0 || err == -EINPROGRESS) && assoc_id) > + if (assoc_id) > *assoc_id = asoc->assoc_id; > + err = sctp_wait_for_connect(asoc, &timeo); > + /* Note: the asoc may be freed after the return of > + * sctp_wait_for_connect. > + */ > > /* Don't free association on exit. */ > asoc = NULL; From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrey Konovalov Date: Thu, 03 Nov 2016 18:45:04 +0000 Subject: Re: net/sctp: use-after-free in __sctp_connect Message-Id: List-Id: References: <20161019165754.GD2958@localhost.localdomain> <20161103175220.GG8514@localhost.localdomain> <20161103183533.GH8514@localhost.localdomain> In-Reply-To: <20161103183533.GH8514@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Marcelo Ricardo Leitner Cc: Vlad Yasevich , Neil Horman , "David S. Miller" , linux-sctp@vger.kernel.org, netdev , LKML , syzkaller , Kostya Serebryany , Alexander Potapenko , Eric Dumazet , Dmitry Vyukov On Thu, Nov 3, 2016 at 7:35 PM, Marcelo Ricardo Leitner wrote: > On Thu, Nov 03, 2016 at 07:02:47PM +0100, Andrey Konovalov wrote: >> On Thu, Nov 3, 2016 at 6:52 PM, Marcelo Ricardo Leitner >> wrote: >> > On Thu, Nov 03, 2016 at 06:11:01PM +0100, Andrey Konovalov wrote: >> >> On Wed, Nov 2, 2016 at 11:42 PM, Andrey Konovalov wrote: >> >> > On Wed, Oct 19, 2016 at 6:57 PM, Marcelo Ricardo Leitner >> >> > wrote: >> >> >> On Wed, Oct 19, 2016 at 02:25:24PM +0200, Andrey Konovalov wrote: >> >> >>> Hi, >> >> >>> >> >> >>> I've got the following error report while running the syzkaller fuzzer: >> >> >>> >> >> >>> ================================= >> >> >>> BUG: KASAN: use-after-free in __sctp_connect+0xabe/0xbf0 at addr >> >> >>> ffff88006b1dc610 >> >> >> >> >> >> Seems this is the same that Dmitry Vyukov had reported back in Jan 13th. >> >> >> So far I couldn't identify the reason. >> >> >> "Good" to know it's still there, thanks for reporting it. >> >> >> >> Hi Marcelo, >> >> >> > >> > Hi >> > >> >> So I've looked at the code. >> >> As far as I understand, the problem is a race condition between >> >> setsockopt(SCTP_SOCKOPT_CONNECTX) and shutdown on an sctp socket. >> >> setsockopt() calls sctp_wait_for_connect(), which exits the for loop >> >> on the sk->sk_shutdown & RCV_SHUTDOWN if clause, and then frees asoc >> >> with sctp_association_put() and returns err = 0. >> >> Then __sctp_connect() checks that err = 0 and reads asoc->assoc_id >> >> from the freed asoc. >> > >> > Suddenly this seems familiar. Your description makes sense, thanks for >> > looking deeper into this, Andrey. >> > >> > This fix should do it, can you please try it? I'll post it properly >> > if it works. >> >> Yes, it fixes the issue. >> >> Tested-by: Andrey Konovalov >> >> Thanks for the fix! > > Ahm this other fix looks better: do the read before calling > sctp_wait_for_connect() as that id won't change in this call and the > application shouldn't trust this number if an error is returned, so > there should be no issues by returning it in such situation. > > Can you please confirm this one also works? Thanks! Sure! This one also works. Tested-by: Andrey Konovalov > > ---8<--- > > diff --git a/net/sctp/socket.c b/net/sctp/socket.c > index 6cdc61c21438..be1d9bb98230 100644 > --- a/net/sctp/socket.c > +++ b/net/sctp/socket.c > @@ -1214,9 +1214,12 @@ static int __sctp_connect(struct sock *sk, > > timeo = sock_sndtimeo(sk, f_flags & O_NONBLOCK); > > - err = sctp_wait_for_connect(asoc, &timeo); > - if ((err = 0 || err = -EINPROGRESS) && assoc_id) > + if (assoc_id) > *assoc_id = asoc->assoc_id; > + err = sctp_wait_for_connect(asoc, &timeo); > + /* Note: the asoc may be freed after the return of > + * sctp_wait_for_connect. > + */ > > /* Don't free association on exit. */ > asoc = NULL;