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

From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: viro@zeniv.linux.org.uk, darrick.wong@oracle.com, tytso@mit.edu,
	adilger.kernel@dilger.ca, clm@fb.com, jbacik@fb.com,
	dsterba@suse.com
Cc: sandeen@sandeen.net, dhowells@redhat.com, fliu@suse.com,
	jack@suse.cz, jeffm@suse.com, nborisov@suse.com,
	jake.norris@suse.com, mtk.manpages@gmail.com,
	linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Luis R. Rodriguez" <mcgrof@kernel.org>
Subject: [RFC v2 3/4] ext4: add verifier check for symlink with append/immutable flags
Date: Thu, 10 May 2018 16:13:58 -0700	[thread overview]
Message-ID: <20180510231359.16899-4-mcgrof@kernel.org> (raw)
In-Reply-To: <20180510231359.16899-1-mcgrof@kernel.org>

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@kernel.org>
---
 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

