linux-ext4 - Re: [PATCH 2/3] ext4: Be more strict when verifying flags set via SETFLAGS ioctls

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Message-ID: <20161129162132.xv66ojffxn7gxllr@thunk.org>
Date:   Tue, 29 Nov 2016 11:21:32 -0500
From:   Theodore Ts'o <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/3] ext4: Be more strict when verifying flags set via
 SETFLAGS ioctls

On Thu, Oct 06, 2016 at 01:04:33PM +0200, Jan Kara wrote:
> Currently we just silently ignore flags that we don't understand (or
> that cannot be manipulated) through EXT4_IOC_SETFLAGS and
> EXT4_IOC_FSSETXATTR ioctls. This makes it problematic for the unused
> flags to be used in future (some app may be inadvertedly setting them
> and we won't notice until the flag gets used). Also this is inconsistent
> with other filesystems like XFS or BTRFS which return EOPNOTSUPP when
> they see a flag they cannot set.
> 
> ext4 has the additional problem that there are flags which are returned
> by EXT4_IOC_GETFLAGS ioctl but which cannot be modified via
> EXT4_IOC_SETFLAGS. So we have to be careful to ignore value of these
> flags and not fail the ioctl when they are set (as e.g. chattr(1) passes
> flags returned from EXT4_IOC_GETFLAGS to EXT4_IOC_SETFLAGS without any
> masking and thus we'd break this utility).
> 
> Signed-off-by: Jan Kara <jack@...e.cz>

Thanks, applied.

					- Ted
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