linux-kernel - Re: [RFC v2 3/4] ext4: add verifier check for symlink with append/immutable flags

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Date:   Fri, 11 May 2018 23:12:18 +0200
From:   Jan Kara <jack@...e.cz>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     viro@...iv.linux.org.uk, darrick.wong@...cle.com, 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 3/4] ext4: add verifier check for symlink with
 append/immutable flags

On Thu 10-05-18 16:13:58, 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 inform the user as the filesystem must be corrupted.
> 
> Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/inode.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 37a2f7a2b66a..6acf0dd6b6e6 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4947,6 +4947,13 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
>  		inode->i_op = &ext4_dir_inode_operations;
>  		inode->i_fop = &ext4_dir_operations;
>  	} else if (S_ISLNK(inode->i_mode)) {
> +		/* VFS does not allow setting these so must be corruption */
> +		if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {
> +			EXT4_ERROR_INODE(inode,
> +			  "immutable or append flags not allowed on symlinks");
> +			ret = -EFSCORRUPTED;
> +			goto bad_inode;
> +		}
>  		if (ext4_encrypted_inode(inode)) {
>  			inode->i_op = &ext4_encrypted_symlink_inode_operations;
>  			ext4_set_aops(inode);
> -- 
> 2.17.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR