[PATCH 1/6] hfsplus: prevent btree data loss on root split

Ernesto A. Fernández
2018-08-31T08:03:48Z

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.

Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
---
fs/hfsplus/brec.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/hfsplus/brec.c b/fs/hfsplus/brec.c
index ed8eacb34452..aa17a392b414 100644
--- a/fs/hfsplus/brec.c
+++ b/fs/hfsplus/brec.c
@@ -429,6 +429,10 @@ static int hfs_brec_update_parent(struct hfs_find_data *fd)
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);
--
2.11.0