hfsplus: fix oops on mount with corrupted btree extent records

A particular fsfuzzer run caused an hfs file system to crash on mount. This
is due to a corrupted MDB extent record causing a miscalculation of
HFSPLUS_I(inode)->first_blocks for the extent tree. If the extent records
are zereod out, then it won't trigger the first_blocks special case and
instead falls through to the extent code, which we're in the middle
of initializing.

This patch catches the 0 size extent records, reports the corruption,
and fails the mount.

[hch: ported of commit 47f365eb575735c6b2edf5d08e0d16d26a9c23bd from hfs]

Reported-by: Ramon de Carvalho Valle <rcvalle@linux.vnet.ibm.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Christoph Hellwig <hch@tuxera.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index 8306479f6b3a..d4bd864ce108 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -39,10 +39,16 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
                 goto free_tree;
         tree->inode = inode;
 
+        if (!HFSPLUS_I(tree->inode)->first_blocks) {
+                printk(KERN_ERR
+                       "hfs: invalid btree extent records (0 size).\n");
+                goto free_inode;
+        }
+
         mapping = tree->inode->i_mapping;
         page = read_mapping_page(mapping, 0, NULL);
         if (IS_ERR(page))
-                goto free_tree;
+                goto free_inode;
 
         /* Load the header */
         head = (struct hfs_btree_header_rec *)(kmap(page) + sizeof(struct hfs_bnode_desc));
@@ -89,8 +95,9 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
  fail_page:
         tree->inode->i_mapping->a_ops = &hfsplus_aops;
         page_cache_release(page);
- free_tree:
+ free_inode:
         iput(tree->inode);
+ free_tree:
         kfree(tree);
         return NULL;
 }