linux-kernel - Re: [v4 PATCH 1/1] init: fix race between rootfs mount and firmware loading

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Date:	Sat, 20 Sep 2014 22:20:27 +0900
From:	Roman Peniaev <r.peniaev@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ming Lei <ming.lei@...onical.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [v4 PATCH 1/1] init: fix race between rootfs mount and firmware loading

Thanks, Oleg, for the review.

--
Roman

On Sat, Sep 20, 2014 at 4:45 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 09/19, Roman Pen wrote:
>>
>> +void wait_for_rootfs(void)
>> +{
>> +     /* Here we try to protect from a few things:
>> +      * 1. Avoid waiting for ourselves, when init thread has not
>> +      *    mounted rootfs yet.
>> +      * 2. Avoid warning if call chain was initiated from userspace
>> +      *    /sbin/init. For example when /sbin/init loads the driver,
>> +      *    which, in turn, wants to access rootfs (e.g. firmware loading),
>> +      *    thus it has to be sure, that rootfs has been successfully
>> +      *    mounted.
>> +      */
>> +     if (rootfs_mounted || WARN_ON(is_global_init(current)))
>> +             return;
>> +     else
>> +             wait_event(rootfs_waitq, rootfs_mounted);
>> +}
>
> Well, in this case __wait_event() makes more sense, we already checked
> rootfs_mounted, but this is minor.
>
> Reviewed-by: Oleg Nesterov <oleg@...hat.com>
>
>
> But I hope that Greg can take a look too. I do not understand the problem
> space enough, so I am not sure this is the "right" fix. Say, perhaps we
> should change the drivers which abuse request_firmware(), or do something
> else.
>
> Oleg.
>
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