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From: Christian Brauner <christian.brauner@ubuntu.com>
To: parri.andrea@gmail.com
Cc: bsingharora@gmail.com, dvyukov@google.com, elver@google.com,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	syzbot+c5d03165a1bd1dead0c1@syzkaller.appspotmail.com,
	syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH] taskstats: fix data-race
Date: Wed, 9 Oct 2019 13:40:41 +0200	[thread overview]
Message-ID: <20191009114040.tqbbdxmkvvt6mia5@wittgenstein> (raw)
In-Reply-To: <20191009113134.5171-1-christian.brauner@ubuntu.com>

On Wed, Oct 09, 2019 at 01:31:34PM +0200, Christian Brauner wrote:
> When assiging and testing taskstats in taskstats_exit() there's a race
> when writing and reading sig->stats when a thread-group with more than
> one thread exits:
> 
> cpu0:
> thread catches fatal signal and whole thread-group gets taken down
>  do_exit()
>  do_group_exit()
>  taskstats_exit()
>  taskstats_tgid_alloc()
> The tasks reads sig->stats without holding sighand lock seeing garbage.
> 
> cpu1:
> task calls exit_group()
>  do_exit()
>  do_group_exit()
>  taskstats_exit()
>  taskstats_tgid_alloc()
> The task takes sighand lock and assigns new stats to sig->stats.
> 
> Fix this by using smp_load_acquire() and smp_store_release().
> 
> Reported-by: syzbot+c5d03165a1bd1dead0c1@syzkaller.appspotmail.com
> Fixes: 34ec12349c8a ("taskstats: cleanup ->signal->stats allocation")
> Cc: stable@vger.kernel.org
> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
> Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

_sigh_, let me resend since i fcked this one up.

Christian

  reply	other threads:[~2019-10-09 11:40 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20191007104039.GA16085@andrea.guest.corp.microsoft.com>
2019-10-07 11:01 ` [PATCH v2] taskstats: fix data-race Christian Brauner
2019-10-07 13:18   ` Andrea Parri
2019-10-07 13:28     ` Christian Brauner
2019-10-07 13:50     ` Dmitry Vyukov
2019-10-07 13:55       ` Christian Brauner
2019-10-07 14:08         ` Dmitry Vyukov
2019-10-07 14:10           ` Christian Brauner
2019-10-07 14:14       ` Andrea Parri
2019-10-07 14:18         ` Dmitry Vyukov
2019-10-08 14:20           ` Andrea Parri
2019-10-08 14:24             ` Christian Brauner
2019-10-08 15:26               ` Andrea Parri
2019-10-08 15:35                 ` Christian Brauner
2019-10-08 15:44                   ` Andrea Parri
2019-10-09 11:31                     ` [PATCH] " Christian Brauner
2019-10-09 11:40                       ` Christian Brauner [this message]
2019-10-09 11:48                       ` [PATCH v5] " Christian Brauner
2019-10-09 12:08                         ` Andrea Parri
2019-10-09 13:26                         ` Christian Brauner
2019-10-21 11:33                         ` [PATCH v6] " Christian Brauner
2019-10-21 12:19                           ` Rasmus Villemoes
2019-10-21 13:04                             ` Christian Brauner
2019-11-29 17:56                               ` Will Deacon
2019-11-30 15:08                                 ` Christian Brauner
2019-10-23 12:16                           ` Andrea Parri
2019-10-23 12:39                             ` Dmitry Vyukov
2019-10-23 13:11                               ` Christian Brauner
2019-10-23 13:20                                 ` Dmitry Vyukov
2019-10-24 11:31                               ` Andrea Parri
2019-10-24 11:51                                 ` Dmitry Vyukov
2019-10-24 13:05                                   ` Andrea Parri
2019-10-24 13:13                                     ` Dmitry Vyukov
2019-10-24 13:21                                       ` Christian Brauner
2019-10-24 13:34                                         ` Dmitry Vyukov
2019-10-24 13:43                                       ` Andrea Parri
2019-10-24 13:58                                         ` Dmitry Vyukov
2019-10-24 14:40                                           ` Andrea Parri
2019-10-24 14:49                                             ` Dmitry Vyukov
2019-11-29 17:57                           ` Will Deacon
2019-10-09 11:48                       ` [PATCH] " Marco Elver
2019-10-09 11:53                         ` Christian Brauner

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