Commit 98cf21c6 authored Mar 25, 2015 by Sergei Antonov Committed by Linus Torvalds Mar 25, 2015

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



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@gmail.com>
Cc: Joe Perches <joe@perches.com>
Reviewed-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Acked-by: 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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 1f31e1b1

fs/hfsplus/brec.c

+11 −9

Original line number	Diff line number	Diff line
		@@ -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
		/*
		* 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)
		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;

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