linux-ext4 - [RFC v2 4/4] btrfs: verify symlinks with append/immutable flags

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Date:   Thu, 10 May 2018 16:13:59 -0700
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     viro@...iv.linux.org.uk, darrick.wong@...cle.com, tytso@....edu,
        adilger.kernel@...ger.ca, clm@...com, jbacik@...com,
        dsterba@...e.com
Cc:     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,
        "Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: [RFC v2 4/4] btrfs: verify symlinks with append/immutable flags

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>
---
 fs/btrfs/inode.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c4bdb597b323..d9c786be408c 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3933,6 +3933,15 @@ static int btrfs_read_locked_inode(struct inode *inode)
 		inode->i_op = &btrfs_dir_inode_operations;
 		break;
 	case S_IFLNK:
+		/* VFS does not allow setting these so must be corruption */
+		if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {
+			ret = -EUCLEAN;
+			btrfs_crit(fs_info,
+				  "corrupt symlink with append/immutable ino=%llu root=%llu\n",
+				  btrfs_ino(BTRFS_I(inode)),
+				  root->root_key.objectid);
+			goto make_bad;
+		}
 		inode->i_op = &btrfs_symlink_inode_operations;
 		inode_nohighmem(inode);
 		inode->i_mapping->a_ops = &btrfs_symlink_aops;
-- 
2.17.0