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From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
To: Xin Long <lucien.xin@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>,
	Vlad Yasevich <vyasevich@gmail.com>,
	Neil Horman <nhorman@tuxdriver.com>,
	"David S. Miller" <davem@davemloft.net>,
	linux-sctp@vger.kernel.org, netdev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	Eric Dumazet <edumazet@google.com>,
	Kostya Serebryany <kcc@google.com>,
	syzkaller <syzkaller@googlegroups.com>
Subject: Re: net/sctp: list double add warning in sctp_endpoint_add_asoc
Date: Wed, 5 Apr 2017 09:44:15 -0300	[thread overview]
Message-ID: <20170405124415.GC911@localhost.localdomain> (raw)
In-Reply-To: <CADvbK_dgD65mygqkGuA85ShBnHrD3y4u_P=XoREyEn7y0J4_+A@mail.gmail.com>

On Wed, Apr 05, 2017 at 06:48:45PM +0800, Xin Long wrote:
> On Wed, Apr 5, 2017 at 5:14 AM, Marcelo Ricardo Leitner
> <marcelo.leitner@gmail.com> wrote:
> > On Wed, Apr 05, 2017 at 01:29:19AM +0800, Xin Long wrote:
> >> On Tue, Apr 4, 2017 at 9:28 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> >> > Hi,
> >> >
> >> > I've got the following error report while fuzzing the kernel with syzkaller.
> >> >
> >> > On commit a71c9a1c779f2499fb2afc0553e543f18aff6edf (4.11-rc5).
> >> >
> >> > A reproducer and .config are attached.
> >> The script is pretty hard to reproduce the issue in my env.
> >
> > I didn't try running it but I also found the reproducer very complicated
> > to follow. Do you have any plans on having some PoC optimizer, so we can
> > have a more readable code?
> > strace is handy for filtering the noise, yes, but sometimes it doesn't
> > cut it.
> I got the script now:
> 1. create sk
> 2. set sk->sndbuf = x
> 3. sendmsg with size s1 (s1 < x)
> 4. sendmsg with size s2 (s1+s2 > x)
> 5. sendmsg with size s3 (wspace < 0), wait sndbuf, schedule out.
> 6. listen sk (abnormal operation on sctp client)
> 7. accept sk.
> 
> In step 6, sk->sk_state = listening, then step 7 could get the first asoc
> from ep->asoc_list and alloc a new sk2, attach the asoc to sk2.
> 
> after a while, sendmsg schedule in, but asoc->sk is sk2, !=sk.
> the same issue we fix for peeloff on commit dfcb9f4f99f1 ("sctp: deny
> peeloff operation on asocs with threads sleeping on it") happens.

Yes. That explains why the asoc isn't dead by when sendmsg comes back,
and avoid that dead check.

> 
> But we should not fix it by the same way as for peeloff. the real reason
> causes this issue is on step 6, it should disallow listen on the established sk.

Agreed.

> 
> The following fix should work for this, just similar with what
> inet_listen() did.
> 
> @@ -7174,6 +7175,9 @@ int sctp_inet_listen(struct socket *sock, int backlog)
>         if (sock->state != SS_UNCONNECTED)
>                 goto out;
> 
> +       if (!sctp_sstate(sk, LISTENING) && !sctp_sstate(sk,CLOSED))
> +               goto out;
> +
> 
> what do you think ?

Yes, agreed.
Thanks!

  Marcelo

WARNING: multiple messages have this Message-ID
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
To: Xin Long <lucien.xin@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>,
	Vlad Yasevich <vyasevich@gmail.com>,
	Neil Horman <nhorman@tuxdriver.com>,
	"David S. Miller" <davem@davemloft.net>,
	linux-sctp@vger.kernel.org, netdev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	Eric Dumazet <edumazet@google.com>,
	Kostya Serebryany <kcc@google.com>,
	syzkaller <syzkaller@googlegroups.com>
Subject: Re: net/sctp: list double add warning in sctp_endpoint_add_asoc
Date: Wed, 05 Apr 2017 12:44:15 +0000	[thread overview]
Message-ID: <20170405124415.GC911@localhost.localdomain> (raw)
In-Reply-To: <CADvbK_dgD65mygqkGuA85ShBnHrD3y4u_P=XoREyEn7y0J4_+A@mail.gmail.com>

On Wed, Apr 05, 2017 at 06:48:45PM +0800, Xin Long wrote:
> On Wed, Apr 5, 2017 at 5:14 AM, Marcelo Ricardo Leitner
> <marcelo.leitner@gmail.com> wrote:
> > On Wed, Apr 05, 2017 at 01:29:19AM +0800, Xin Long wrote:
> >> On Tue, Apr 4, 2017 at 9:28 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> >> > Hi,
> >> >
> >> > I've got the following error report while fuzzing the kernel with syzkaller.
> >> >
> >> > On commit a71c9a1c779f2499fb2afc0553e543f18aff6edf (4.11-rc5).
> >> >
> >> > A reproducer and .config are attached.
> >> The script is pretty hard to reproduce the issue in my env.
> >
> > I didn't try running it but I also found the reproducer very complicated
> > to follow. Do you have any plans on having some PoC optimizer, so we can
> > have a more readable code?
> > strace is handy for filtering the noise, yes, but sometimes it doesn't
> > cut it.
> I got the script now:
> 1. create sk
> 2. set sk->sndbuf = x
> 3. sendmsg with size s1 (s1 < x)
> 4. sendmsg with size s2 (s1+s2 > x)
> 5. sendmsg with size s3 (wspace < 0), wait sndbuf, schedule out.
> 6. listen sk (abnormal operation on sctp client)
> 7. accept sk.
> 
> In step 6, sk->sk_state = listening, then step 7 could get the first asoc
> from ep->asoc_list and alloc a new sk2, attach the asoc to sk2.
> 
> after a while, sendmsg schedule in, but asoc->sk is sk2, !=sk.
> the same issue we fix for peeloff on commit dfcb9f4f99f1 ("sctp: deny
> peeloff operation on asocs with threads sleeping on it") happens.

Yes. That explains why the asoc isn't dead by when sendmsg comes back,
and avoid that dead check.

> 
> But we should not fix it by the same way as for peeloff. the real reason
> causes this issue is on step 6, it should disallow listen on the established sk.

Agreed.

> 
> The following fix should work for this, just similar with what
> inet_listen() did.
> 
> @@ -7174,6 +7175,9 @@ int sctp_inet_listen(struct socket *sock, int backlog)
>         if (sock->state != SS_UNCONNECTED)
>                 goto out;
> 
> +       if (!sctp_sstate(sk, LISTENING) && !sctp_sstate(sk,CLOSED))
> +               goto out;
> +
> 
> what do you think ?

Yes, agreed.
Thanks!

  Marcelo

  reply	other threads:[~2017-04-05 12:44 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-04 13:28 Andrey Konovalov
2017-04-04 17:29 ` Xin Long
2017-04-04 17:29   ` Xin Long
2017-04-04 21:14   ` Marcelo Ricardo Leitner
2017-04-04 21:14     ` Marcelo Ricardo Leitner
2017-04-05 10:48     ` Xin Long
2017-04-05 10:48       ` Xin Long
2017-04-05 12:44       ` Marcelo Ricardo Leitner [this message]
2017-04-05 12:44         ` Marcelo Ricardo Leitner
2017-04-05 14:03         ` Andrey Konovalov
2017-04-05 14:03           ` Andrey Konovalov
2017-04-05 14:02     ` Andrey Konovalov
2017-04-05 14:02       ` Andrey Konovalov
2017-04-05 14:22       ` Marcelo Ricardo Leitner
2017-04-05 14:22         ` Marcelo Ricardo Leitner

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