From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
lkml <linux-kernel@vger.kernel.org>, Kay Sievers <kay@vrfy.org>,
syzbot <syzbot+f648cfb7e0b52bf7ae32@syzkaller.appspotmail.com>
Subject: Re: [PATCH] kobject: Don't trigger kobject_uevent(KOBJ_REMOVE) twice.
Date: Thu, 21 Feb 2019 19:40:20 +0900 [thread overview]
Message-ID: <bd8cc4bb-4c58-dbad-a012-3193a41dc0ca@i-love.sakura.ne.jp> (raw)
In-Reply-To: <CAKdAkRSjZB5MJ=vPwDTUouTTYF5Gu1d7iWjzdOzd+w5HJ=1CFQ@mail.gmail.com>
On 2019/02/21 4:52, Dmitry Torokhov wrote:
> On Wed, Feb 20, 2019 at 7:07 AM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
>> But I would argue that this is not ok, as the remove uevent did NOT get
>> sent, and you are saying it did.
>
> "It is the thought that counts" here. The code was added to catch
> cases where nobody even attempted to send "remove" uevents. It does
> not guarantee that an event will ultimately be sent (we are at the
> point of no return as far as the rest of the kernel is concerned,
> there are no repeats or do-overs).
>
>>
>> What memory is being used-after-free here when we fail to properly send
>> a uevent? Shouldn't we fix up that problem correctly?
It is explained at https://lkml.kernel.org/r/20190219185558.GA210481@dtor-ws .
>
> This is the correct fix (in spirit, we may argue about whether it is
> valid to call the flag "state_add_uevent_sent" now or we should or
> collapse both it and "state_add_uevent_sent" into
> "need_send_remove_uevent"). Other subsystems are in their own right to
> not expect to get uvent callbacks past the point of calling
> device_del() as they are tearing down parts of the device environment
> (even though the device structure may stay in memory for a while).
>
> Thanks.
Which subsystems benefit from commit 0f4dafc0563c6c49 ("Kobject: auto-cleanup
on final unref") ? If there is no such subsystem, it will be better to remove
state_add_uevent_sent and state_remove_uevent_sent logic.
next prev parent reply other threads:[~2019-02-21 10:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-20 13:38 [PATCH] kobject: Don't trigger kobject_uevent(KOBJ_REMOVE) twice Tetsuo Handa
2019-02-20 15:07 ` Greg Kroah-Hartman
2019-02-20 19:52 ` Dmitry Torokhov
2019-02-21 10:40 ` Tetsuo Handa [this message]
2019-02-21 11:09 ` Greg Kroah-Hartman
2019-02-21 12:31 ` Tetsuo Handa
2019-02-27 10:21 ` Tetsuo Handa
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