[3.13.y-ckt stable] Patch "hfsplus: fix B-tree corruption after insertion at position 0" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt20.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From b5ef8af21cad50e8432cc20f291ed8c2b0865a17 Mon Sep 17 00:00:00 2001
From: Sergei Antonov <saproj at gmail.com>
Date: Wed, 25 Mar 2015 15:55:34 -0700
Subject: 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.

Signed-off-by: Sergei Antonov <saproj at gmail.com>
Cc: Joe Perches <joe at perches.com>
Reviewed-by: Vyacheslav Dubeyko <slava at dubeyko.com>
Acked-by: Hin-Tak Leung <htl10 at users.sourceforge.net>
Cc: Anton Altaparmakov <aia21 at cam.ac.uk>
Cc: Al Viro <viro at zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch at infradead.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/hfsplus/brec.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/fs/hfsplus/brec.c b/fs/hfsplus/brec.c
index 6e560d5..754fdf8 100644
--- a/fs/hfsplus/brec.c
+++ b/fs/hfsplus/brec.c
@@ -131,13 +131,16 @@ 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);
@@ -168,9 +171,6 @@ skip:
 		goto again;
 	}

-	if (!rec)
-		hfs_brec_update_parent(fd);
-
 	return 0;
 }

@@ -370,6 +370,8 @@ again:
 	if (IS_ERR(parent))
 		return PTR_ERR(parent);
 	__hfs_brec_find(parent, fd, hfs_find_rec_by_key);
+	if (fd->record < 0)
+		return -ENOENT;
 	hfs_bnode_dump(parent);
 	rec = fd->record;

--
1.9.1