linux-kernel - Re: [RFC v2 2/4] xfs: add verifier check for symlink with append/immutable flags

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Message-ID: <20180511022020.GG11261@magnolia>
Date:   Thu, 10 May 2018 19:20:20 -0700
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     viro@...iv.linux.org.uk, tytso@....edu, adilger.kernel@...ger.ca,
        clm@...com, jbacik@...com, dsterba@...e.com, sandeen@...deen.net,
        dhowells@...hat.com, fliu@...e.com, jack@...e.cz, jeffm@...e.com,
        nborisov@...e.com, jake.norris@...e.com, mtk.manpages@...il.com,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 2/4] xfs: add verifier check for symlink with
 append/immutable flags

On Thu, May 10, 2018 at 04:13:57PM -0700, Luis R. Rodriguez wrote:
> The Linux VFS does not allow a way to set append/immuttable attributes
> to symlinks, this is just not possible. If this is detected we can
> correct this with xfs_repair, so inform the user.
> 
> Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
> ---
>  fs/xfs/libxfs/xfs_symlink_remote.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_symlink_remote.c b/fs/xfs/libxfs/xfs_symlink_remote.c
> index 5ef5f354587e..42dd81ede3d6 100644
> --- a/fs/xfs/libxfs/xfs_symlink_remote.c
> +++ b/fs/xfs/libxfs/xfs_symlink_remote.c
> @@ -242,5 +242,10 @@ xfs_symlink_shortform_verify(
>  	/* We /did/ null-terminate the buffer, right? */
>  	if (*endp != 0)
>  		return __this_address;
> +
> +	/* Immutable and append flags are not allowed on symlinks */
> +	if (ip->i_d.di_flags & (XFS_DIFLAG_APPEND | XFS_DIFLAG_IMMUTABLE))
> +		return __this_address;

This belongs in xfs_dinode_verify so that it checks all symlinks, not
just the one shortform ones.

--D

> +
>  	return NULL;
>  }
> -- 
> 2.17.0
> 
> --
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