Commit 3eb548ee authored Sep 14, 2016 by Liu Bo Committed by David Sterba Sep 26, 2016

Btrfs: memset to avoid stale content in btree node block



During updating btree, we could push items between sibling
nodes/leaves, for leaves data sections starts reversely from
the end of the block while for nodes we only have key pairs
which are stored one by one from the start of the block.

So we could do try to push key pairs from one node to the next
node right in the tree, and after that, we update the node's
nritems to reflect the correct end while leaving the stale
content in the node.  One may intentionally corrupt the fs
image and access the stale content by bumping the nritems and
causes various crashes.

This takes the in-memory @nritems as the correct one and
gets to memset the unused part of a btree node.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent 3561b9db

fs/btrfs/extent_io.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -3732,6 +3732,17 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
		if (btrfs_header_owner(eb) == BTRFS_TREE_LOG_OBJECTID)
		bio_flags = EXTENT_BIO_TREE_LOG;

		/* set btree node beyond nritems with 0 to avoid stale content */
		if (btrfs_header_level(eb) > 0) {
		u32 nritems;
		unsigned long end;

		nritems = btrfs_header_nritems(eb);
		end = btrfs_node_key_ptr_offset(nritems);

		memset_extent_buffer(eb, 0, end, eb->len - end);
		}

		for (i = 0; i < num_pages; i++) {
		struct page *p = eb->pages[i];

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