hfs: handle more on-disk corruptions without oopsing

hfs seems prone to bad things when it encounters on disk corruption.  Many
values are read from disk, and used as lengths to memcpy, as an example.
This patch fixes up several of these problematic cases.

o sanity check the on-disk maximum key lengths on mount
  (these are set to a defined value at mkfs time and shouldn't differ)
o check on-disk node keylens against the maximum key length for each tree
o fix hfs_btree_open so that going out via free_tree: doesn't wind
  up in hfs_releasepage, which wants to follow the very pointer
  we were trying to set up:
	HFS_SB(sb)->cat_tree = hfs_btree_open()
		...
		failure gets to hfs_releasepage and tries
		to follow HFS_SB(sb)->cat_tree

Tested with the fsfuzzer; it survives more than it used to.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 1 deletions

diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c
index 8a3a650..31284c7 100644
--- a/fs/hfs/btree.c
+++ b/fs/hfs/btree.c
@@ -81,6 +81,17 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke
 		goto fail_page;
 	if (!tree->node_count)
 		goto fail_page;
+	if ((id == HFS_EXT_CNID) && (tree->max_key_len != HFS_MAX_EXT_KEYLEN)) {
+		printk(KERN_ERR "hfs: invalid extent max_key_len %d\n",
+			tree->max_key_len);
+		goto fail_page;
+	}
+	if ((id == HFS_CAT_CNID) && (tree->max_key_len != HFS_MAX_CAT_KEYLEN)) {
+		printk(KERN_ERR "hfs: invalid catalog max_key_len %d\n",
+			tree->max_key_len);
+		goto fail_page;
+	}
+
 	tree->node_size_shift = ffs(size) - 1;
 	tree->pages_per_bnode = (tree->node_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 
@@ -89,9 +100,9 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke
 	return tree;
 
  fail_page:
-	tree->inode->i_mapping->a_ops = &hfs_aops;
 	page_cache_release(page);
  free_tree:
+	tree->inode->i_mapping->a_ops = &hfs_aops;
 	iput(tree->inode);
 	kfree(tree);
 	return NULL;