All of lore.kernel.org
 help / color / mirror / Atom feed
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: Tue, 4 Apr 2017 18:14:54 -0300	[thread overview]
Message-ID: <20170404211454.GA911@localhost.localdomain> (raw)
In-Reply-To: <CADvbK_f1FEGRnucuMkQT6RKm0G1tKcfHyj=-GqxgzQ4iQoBLCg@mail.gmail.com>

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.

> But there seems a case to cause a use-after-free when out of snd_buf.
> 
> the case is like:
> -----------
> one thread:                       another thread:
>                                   sctp_rcv hold asoc (hold transport)
>                                   enqueue the chunk to backlog queue
>                                   [refcnt=2]
> 
> sctp_close free assoc
> [refcnt=1]
> 
> sctp_sendmsg find asoc
> but not hold it
> 
> out of snd_buf
> hold asoc, schedule out
> [refcnt = 2]
> 
>                                   process backlog and put asoc/transport
>                                   [refcnt=1]
> 
> schedule in, put asoc
> [refcnt=0] <--- destroyed
> 
> sctp_sendmsg continue

It shouldn't be continuing here because sctp_wait_for_sndbuf and
sctp_wait_for_connect functions are checking if the asoc is dead
already when it schedules in, even though sctp_wait_for_connect return
value is ignored and sctp_sendmsg() simply returns after that.
Or the checks for dead asocs in there aren't enough somehow.

> using asoc, panic

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: Tue, 04 Apr 2017 21:14:54 +0000	[thread overview]
Message-ID: <20170404211454.GA911@localhost.localdomain> (raw)
In-Reply-To: <CADvbK_f1FEGRnucuMkQT6RKm0G1tKcfHyj=-GqxgzQ4iQoBLCg@mail.gmail.com>

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.

> But there seems a case to cause a use-after-free when out of snd_buf.
> 
> the case is like:
> -----------
> one thread:                       another thread:
>                                   sctp_rcv hold asoc (hold transport)
>                                   enqueue the chunk to backlog queue
>                                   [refcnt=2]
> 
> sctp_close free assoc
> [refcnt=1]
> 
> sctp_sendmsg find asoc
> but not hold it
> 
> out of snd_buf
> hold asoc, schedule out
> [refcnt = 2]
> 
>                                   process backlog and put asoc/transport
>                                   [refcnt=1]
> 
> schedule in, put asoc
> [refcnt=0] <--- destroyed
> 
> sctp_sendmsg continue

It shouldn't be continuing here because sctp_wait_for_sndbuf and
sctp_wait_for_connect functions are checking if the asoc is dead
already when it schedules in, even though sctp_wait_for_connect return
value is ignored and sctp_sendmsg() simply returns after that.
Or the checks for dead asocs in there aren't enough somehow.

> using asoc, panic



  reply	other threads:[~2017-04-04 21:15 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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170404211454.GA911@localhost.localdomain \
    --to=marcelo.leitner@gmail.com \
    --cc=andreyknvl@google.com \
    --cc=davem@davemloft.net \
    --cc=dvyukov@google.com \
    --cc=edumazet@google.com \
    --cc=kcc@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-sctp@vger.kernel.org \
    --cc=lucien.xin@gmail.com \
    --cc=netdev@vger.kernel.org \
    --cc=nhorman@tuxdriver.com \
    --cc=syzkaller@googlegroups.com \
    --cc=vyasevich@gmail.com \
    --subject='Re: net/sctp: list double add warning in sctp_endpoint_add_asoc' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.