From: Ernesto A. Fernández <ernesto.mnd.fernandez@xxxxxxxxx> Subject: hfs: prevent btree data loss on root split This 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. It is not possible for this to happen on a valid hfs filesystem because the index nodes have fixed length keys. For reasons I ignore, the hfs module does have support for a number of hfsplus features. A corrupt btree header may report variable length keys and trigger this bug, so it's better to fix it. Link: http://lkml.kernel.org/r/9750b1415685c4adca10766895f6d5ef12babdb0.1535682463.git.ernesto.mnd.fernandez@xxxxxxxxx Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@xxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/hfs/brec.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/fs/hfs/brec.c~hfs-prevent-btree-data-loss-on-root-split +++ a/fs/hfs/brec.c @@ -425,6 +425,10 @@ 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); _
