[PATCH 4.9 04/46] hfsplus: prevent btree data loss on root split

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 0a3021d4f5295aa073c7bf5c5e4de60a2e292578 ]

Creating, renaming or deleting a file may cause catalog corruption and
data loss.  This bug is randomly triggered by xfstests generic/027, but
here is a faster reproducer:

  truncate -s 50M fs.iso
  mkfs.hfsplus fs.iso
  mount fs.iso /mnt
  i=100
  while [ $i -le 150 ]; do
    touch /mnt/$i &>/dev/null
    ((++i))
  done
  i=100
  while [ $i -le 150 ]; do
    mv /mnt/$i /mnt/$(perl -e "print $i x82") &>/dev/null
    ((++i))
  done
  umount /mnt
  fsck.hfsplus -n fs.iso

The bug is triggered whenever hfs_brec_update_parent() needs to split the
root node.  The height of the btree is not increased, which leaves the new
node orphaned and its records lost.

Link: http://lkml.kernel.org/r/26d882184fc43043a810114258f45277752186c7.1535682461.git.ernesto.mnd.fernandez@gmail.com
Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/hfsplus/brec.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/hfsplus/brec.c b/fs/hfsplus/brec.c
index 754fdf8c6356..1002a0c08319 100644
--- a/fs/hfsplus/brec.c
+++ b/fs/hfsplus/brec.c
@@ -427,6 +427,10 @@ skip:
 	if (new_node) {
 		__be32 cnid;
 
+		if (!new_node->parent) {
+			hfs_btree_inc_height(tree);
+			new_node->parent = tree->root;
+		}
 		fd->bnode = hfs_bnode_find(tree, new_node->parent);
 		/* create index key and entry */
 		hfs_bnode_read_key(new_node, fd->search_key, 14);
-- 
2.17.1