hfsplus: fix B-tree corruption after insertion at position 0

commit 98cf21c61a7f5419d82f847c4d77bf6e96a76f5f upstream.

Fix B-tree corruption when a new record is inserted at position 0 in the node
in hfs_brec_insert(). In this case a hfs_brec_update_parent() is called to
update the parent index node (if exists) and it is passed hfs_find_data with
a search_key containing a newly inserted key instead of the key to be updated.
This results in an inconsistent index node. The bug reproduces on my machine
after an extents overflow record for the catalog file (CNID=4) is inserted into
the extents overflow B-tree. Because of a low (reserved) value of CNID=4, it
has to become the first record in the first leaf node.
The resulting first leaf node is correct:
----------------------------------------------------
| key0.CNID=4 | key1.CNID=123 | key2.CNID=456, ... |
----------------------------------------------------
But the parent index key0 still contains the previous key CNID=123:
-----------------------
| key0.CNID=123 | ... |
-----------------------

A change in hfs_brec_insert() makes hfs_brec_update_parent() work correctly
by preventing it from getting fd->record=-1 value from __hfs_brec_find().

Along the way, I removed duplicate code with unification of the if condition.
The resulting code is equivalent to the original code because node is never 0.

Also hfs_brec_update_parent() will now return an error after getting a negative
fd->record value. However, the return value of hfs_brec_update_parent() is not
checked anywhere in the file and I'm leaving it unchanged by this patch.
brec.c lacks error checking after some other calls too, but this issue is of
less importance than the one being fixed by this patch.

Cc: stable@vger.kernel.org
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Hin-Tak Leung <htl10@users.sourceforge.net>
Cc: Anton Altaparmakov <aia21@cam.ac.uk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Sergei Antonov <saproj@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

1 files changed, 11 insertions, 9 deletions

diff --git a/fs/hfsplus/brec.c b/fs/hfsplus/brec.c
index c88e5d72a402ae..5bcf7309937a1d 100644
--- a/fs/hfsplus/brec.c
+++ b/fs/hfsplus/brec.c
@@ -119,13 +119,16 @@ skip:
 	hfs_bnode_write(node, entry, data_off + key_len, entry_len);
 	hfs_bnode_dump(node);
 
-	if (new_node) {
-		/* update parent key if we inserted a key
-		 * at the start of the first node
-		 */
-		if (!rec && new_node != node)
-			hfs_brec_update_parent(fd);
+	/*
+	 * update parent key if we inserted a key
+	 * at the start of the node and it is not the new node
+	 */
+	if (!rec && new_node != node) {
+		hfs_bnode_read_key(node, fd->search_key, data_off + size);
+		hfs_brec_update_parent(fd);
+	}
 
+	if (new_node) {
 		hfs_bnode_put(fd->bnode);
 		if (!new_node->parent) {
 			hfs_btree_inc_height(tree);
@@ -154,9 +157,6 @@ skip:
 		goto again;
 	}
 
-	if (!rec)
-		hfs_brec_update_parent(fd);
-
 	return 0;
 }
 
@@ -341,6 +341,8 @@ again:
 	if (IS_ERR(parent))
 		return PTR_ERR(parent);
 	__hfs_brec_find(parent, fd);
+	if (fd->record < 0)
+		return -ENOENT;
 	hfs_bnode_dump(parent);
 	rec = fd->record;