linux-ext4 - Re: [PATCH 1/5] ext4: preserve i_mode if __ext4_set

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Message-ID: <20170731024447.h4fiawhm6lcavahk@thunk.org>
Date:   Sun, 30 Jul 2017 22:44:47 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Ernesto A. Fernández 
        <ernesto.mnd.fernandez@...il.com>
Cc:     Jan Kara <jack@...e.com>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Dave Kleikamp <shaggy@...nel.org>, linux-ext4@...r.kernel.org,
        jfs-discussion@...ts.sourceforge.net,
        reiserfs-devel@...r.kernel.org
Subject: Re: [PATCH 1/5] ext4: preserve i_mode if __ext4_set_acl() fails

On Wed, Jul 12, 2017 at 06:53:51AM -0300, Ernesto A. Fernández wrote:
> When changing a file's acl mask, __ext4_set_acl() will first set the group
> bits of i_mode to the value of the mask, and only then set the actual
> extended attribute representing the new acl.
> 
> If the second part fails (due to lack of space, for example) and the file
> had no acl attribute to begin with, the system will from now on assume
> that the mask permission bits are actual group permission bits, potentially
> granting access to the wrong users.
> 
> Prevent this by only changing the inode mode after the acl has been set.
> 
> Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@...il.com>

Thanks, applied.

						- Ted