linux-ext4 - Re: [PATCH RESEND] ext4: reinforce check of i_dtime when clearing high fields of uid and gid

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Date:   Mon, 5 Sep 2016 23:01:27 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Daeho Jeong <daeho.jeong@...sung.com>
Cc:     linux-ext4@...r.kernel.org, Hobin Woo <hobin.woo@...sung.com>
Subject: Re: [PATCH RESEND] ext4: reinforce check of i_dtime when clearing
 high fields of uid and gid

On Mon, Aug 22, 2016 at 02:51:25PM +0900, Daeho Jeong wrote:
> Now, ext4_do_update_inode() clears high 16-bit fields of uid/gid
> of deleted and evicted inode to fix up interoperability with old
> kernels. However, it checks only i_dtime of an inode to determine
> whether the inode was deleted and evicted, and this is very risky,
> because i_dtime can be used for the pointer maintaining orphan inode
> list, too. We need to further check whether the i_dtime is being
> used for the orphan inode list even if the i_dtime is not NULL.
> 
> We found that high 16-bit fields of uid/gid of inode are unintentionally
> and permanently cleared when the inode truncation is just triggered,
> but not finished, and the inode metadata, whose high uid/gid bits are
> cleared, is written on disk, and the sudden power-off follows that
> in order.
> 
> Signed-off-by: Daeho Jeong <daeho.jeong@...sung.com>
> Signed-off-by: Hobin Woo <hobin.woo@...sung.com>

Thanks, applied.

						- Ted
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