hfsplus: prevent btree data loss on root split

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>

diff --git a/fs/hfsplus/brec.c b/fs/hfsplus/brec.c
index ed8eacb34452f02107c253c3d57a9c89532daa93..aa17a392b4140910a88192181356a998e828fcef 100644 (file)
--- a/fs/hfsplus/brec.c
+++ b/fs/hfsplus/brec.c
@@ -429,6 +429,10 @@ 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);