From: Greg KH <gregkh@linuxfoundation.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
arnd@arndb.de, linux-kernel@vger.kernel.org,
linux-pm@vger.kernel.org,
Wedson Almeida Filho <wedsonaf@google.com>
Subject: Re: [PATCH] char: misc: make misc_open() and misc_register() killable
Date: Tue, 5 Jul 2022 07:37:21 +0200 [thread overview]
Message-ID: <YsPOEYU7ZqmpD8dw@kroah.com> (raw)
In-Reply-To: <617f64e3-74c8-f98b-3430-bd476867e483@I-love.SAKURA.ne.jp>
On Tue, Jul 05, 2022 at 02:21:17PM +0900, Tetsuo Handa wrote:
> On 2022/07/04 23:31, Greg KH wrote:
> > I don't understand what you are trying to "fix" here. What is userspace
> > doing (as a normal user) that is causing a problem, and what problem is
> > it causing and for what device/hardware/driver is this a problem?
>
> Currently the root cause is unknown.
> This might be another example of deadlock hidden by device_initialize().
>
> We can see from https://syzkaller.appspot.com/text?tag=CrashReport&x=11feb7e0080000 that
> when khungtaskd reports that a process is blocked waiting for misc_mtx at misc_open(),
> there is a process which is holding system_transition_mutex from snapshot_open().
/dev/snapshot is not read/writable by anyone but root for obvious
reasons.
And perhaps it's something that syzbot shouldn't be fuzzing unless it
wants to take the system down easily :)
thanks,
greg k-h
next prev parent reply other threads:[~2022-07-05 5:37 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-13 12:38 INFO: task hung in misc_open (4) syzbot
2022-07-04 6:44 ` [PATCH] char: misc: make misc_open() and misc_register() killable Tetsuo Handa
2022-07-04 7:29 ` Greg KH
2022-07-04 10:25 ` Tetsuo Handa
2022-07-04 11:01 ` Greg KH
2022-07-04 12:34 ` Tetsuo Handa
2022-07-04 12:59 ` Wedson Almeida Filho
2022-07-04 13:48 ` Tetsuo Handa
2022-07-04 13:57 ` Wedson Almeida Filho
2022-07-04 14:07 ` Tetsuo Handa
2022-07-04 14:46 ` Wedson Almeida Filho
2022-07-04 14:31 ` Greg KH
2022-07-05 5:21 ` Tetsuo Handa
2022-07-05 5:37 ` Greg KH [this message]
[not found] ` <a1fcc07e-51ef-eaad-f14b-33f1263e45ac@I-love.SAKURA.ne.jp>
2022-07-05 7:20 ` Dmitry Vyukov
2022-07-05 10:10 ` Greg Kroah-Hartman
2022-07-08 6:06 ` Dmitry Vyukov
2022-07-05 14:01 ` Tetsuo Handa
2022-07-05 14:16 ` Greg KH
2022-07-05 14:35 ` Tetsuo Handa
2022-07-06 6:21 ` Tetsuo Handa
2022-07-06 6:34 ` Greg KH
2022-07-06 10:26 ` Tetsuo Handa
2022-07-06 11:04 ` Oliver Neukum
2022-07-07 5:06 ` Tetsuo Handa
2022-07-07 8:04 ` Greg KH
2022-07-08 13:37 ` Greg KH
2022-07-10 2:27 ` Tetsuo Handa
2022-07-06 12:17 ` Oliver Neukum
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