From: Eric Sandeen <sandeen@redhat.com>
Date: Tue, 15 Jan 2008 13:38:14 -0600
Subject: [fs] hfs: make robust to deal with disk corruption
Message-id: 478D0BA6.9060400@redhat.com
O-Subject: Re: [RHEL5.2 PATCH] UPDATED: make hfs more robust in the face of disk corruption
Bugzilla: 213773

For: Bugzilla Bug 213773: fsfuzz hfs oops'es kernel on ppc

(aside: does anyone know *why* we ship hfs in RHEL?)

This patch was sent upstream... today.

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>

Acked-by: Josef Bacik <jbacik@redhat.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>

diff --git a/fs/hfs/bfind.c b/fs/hfs/bfind.c
index f13f149..4129cdb 100644
--- a/fs/hfs/bfind.c
+++ b/fs/hfs/bfind.c
@@ -52,6 +52,10 @@ int __hfs_brec_find(struct hfs_bnode *bnode, struct hfs_find_data *fd)
 		rec = (e + b) / 2;
 		len = hfs_brec_lenoff(bnode, rec, &off);
 		keylen = hfs_brec_keylen(bnode, rec);
+		if (keylen == 0) {
+			res = -EINVAL;
+			goto fail;
+		}
 		hfs_bnode_read(bnode, fd->key, off, keylen);
 		cmpval = bnode->tree->keycmp(fd->key, fd->search_key);
 		if (!cmpval) {
@@ -67,6 +71,10 @@ int __hfs_brec_find(struct hfs_bnode *bnode, struct hfs_find_data *fd)
 	if (rec != e && e >= 0) {
 		len = hfs_brec_lenoff(bnode, e, &off);
 		keylen = hfs_brec_keylen(bnode, e);
+		if (keylen == 0) {
+			res = -EINVAL;
+			goto fail;
+		}
 		hfs_bnode_read(bnode, fd->key, off, keylen);
 	}
 done:
@@ -75,6 +83,7 @@ done:
 	fd->keylength = keylen;
 	fd->entryoffset = off + keylen;
 	fd->entrylength = len - keylen;
+fail:
 	return res;
 }
 
@@ -198,6 +207,10 @@ int hfs_brec_goto(struct hfs_find_data *fd, int cnt)
 
 	len = hfs_brec_lenoff(bnode, fd->record, &off);
 	keylen = hfs_brec_keylen(bnode, fd->record);
+	if (keylen == 0) {
+		res = -EINVAL;
+		goto out;
+	}
 	fd->keyoffset = off;
 	fd->keylength = keylen;
 	fd->entryoffset = off + keylen;
diff --git a/fs/hfs/brec.c b/fs/hfs/brec.c
index 5c87cf4..878bf25 100644
--- a/fs/hfs/brec.c
+++ b/fs/hfs/brec.c
@@ -44,10 +44,21 @@ u16 hfs_brec_keylen(struct hfs_bnode *node, u16 rec)
 		recoff = hfs_bnode_read_u16(node, node->tree->node_size - (rec + 1) * 2);
 		if (!recoff)
 			return 0;
-		if (node->tree->attributes & HFS_TREE_BIGKEYS)
+		if (node->tree->attributes & HFS_TREE_BIGKEYS) {
 			retval = hfs_bnode_read_u16(node, recoff) + 2;
-		else
+			if (retval > node->tree->max_key_len + 2) {
+				printk(KERN_ERR "hfs: keylen %d too large\n",
+					retval);
+				retval = 0;
+			}
+		} else {
 			retval = (hfs_bnode_read_u8(node, recoff) | 1) + 1;
+			if (retval > node->tree->max_key_len + 1) {
+				printk(KERN_ERR "hfs: keylen %d too large\n",
+					retval);
+				retval = 0;
+			}
+		}
 	}
 	return retval;
 }
diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c
index 4003579..906de2c 100644
--- a/fs/hfs/btree.c
+++ b/fs/hfs/btree.c
@@ -61,7 +61,7 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke
 	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));
@@ -81,6 +81,25 @@ 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;
+	switch (id) {
+	case HFS_EXT_CNID:
+		if (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;
+		}
+		break;
+	case HFS_CAT_CNID:
+		if (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;
+		}
+		break;
+	default:
+		BUG();
+	}
+
 	tree->node_size_shift = ffs(size) - 1;
 	tree->pages_per_bnode = (tree->node_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 
@@ -88,11 +107,12 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke
 	page_cache_release(page);
 	return tree;
 
- fail_page:
-	tree->inode->i_mapping->a_ops = &hfs_aops;
+fail_page:
 	page_cache_release(page);
- free_tree:
+free_inode:
+	tree->inode->i_mapping->a_ops = &hfs_aops;
 	iput(tree->inode);
+free_tree:
 	kfree(tree);
 	return NULL;
 }
diff --git a/fs/hfs/hfs.h b/fs/hfs/hfs.h
index 88099ab..c984cf7 100644
--- a/fs/hfs/hfs.h
+++ b/fs/hfs/hfs.h
@@ -169,6 +169,9 @@ typedef union hfs_btree_key {
 	struct hfs_ext_key ext;
 } hfs_btree_key;
 
+#define HFS_MAX_CAT_KEYLEN	(sizeof(struct hfs_cat_key) - sizeof(u8))
+#define HFS_MAX_EXT_KEYLEN	(sizeof(struct hfs_ext_key) - sizeof(u8))
+
 typedef union hfs_btree_key btree_key;
 
 struct hfs_extent {