linux-kernel - Re: [BUG] fs/aio: A possible sleep-in-atomic bug in aio

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Message-ID: <20171007023152.GQ21978@ZenIV.linux.org.uk>
Date:   Sat, 7 Oct 2017 03:31:52 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Jia-Ju Bai <baijiaju1990@....com>
Cc:     bcrl@...ck.org, linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [BUG] fs/aio: A possible sleep-in-atomic bug in aio_migratepage

On Sat, Oct 07, 2017 at 09:36:48AM +0800, Jia-Ju Bai wrote:
> According to fs/aio.c, cond_resched is called under a spinlock,
> and the function call path is:
> aio_migratepage (acquire the spinlock)
>   migrate_page_copy
>     copy_huge_page
>       __copy_gigantic_page
>         cond_resched
>           might_sleep
> 
> This bug is found by my static analysis tool and my code review.
> A possible fix is to remove cond_resched in __copy_gigantic_page.

How the hell would a huge page end up in page cache of inode created
by aio_private_file()???