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Commit 2849a854 authored by Chris Mason's avatar Chris Mason
Browse files

btrfs: fix use after free iterating extrefs 



The code for btrfs inode-resolve has never worked properly for
files with enough hard links to trigger extrefs.  It was trying to
get the leaf out of a path after freeing the path:

	btrfs_release_path(path);
	leaf = path->nodes[0];
	item_size = btrfs_item_size_nr(leaf, slot);

The fix here is to use the extent buffer we cloned just a little higher
up to avoid deadlocks caused by using the leaf in the path.

Signed-off-by: default avatarChris Mason <clm@fb.com>
cc: stable@vger.kernel.org # v3.7+
cc: Mark Fasheh <mfasheh@suse.de>
Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarMark Fasheh <mfasheh@suse.de>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 849ef928

fs/btrfs/backref.c

+3 −5
Original line number Diff line number Diff line
@@ -1834,7 +1834,6 @@ static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root, 
	int found = 0;

	struct extent_buffer *eb;

	struct btrfs_inode_extref *extref;

	struct extent_buffer *leaf;

	u32 item_size;

	u32 cur_offset;

	unsigned long ptr;
@@ -1862,9 +1861,8 @@ static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root, 
		btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);

		btrfs_release_path(path);



		leaf = path->nodes[0];

		item_size = btrfs_item_size_nr(leaf, slot);

		ptr = btrfs_item_ptr_offset(leaf, slot);

		item_size = btrfs_item_size_nr(eb, slot);

		ptr = btrfs_item_ptr_offset(eb, slot);

		cur_offset = 0;



		while (cur_offset < item_size) {
@@ -1878,7 +1876,7 @@ static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root, 
			if (ret)

				break;



			cur_offset += btrfs_inode_extref_name_len(leaf, extref);

			cur_offset += btrfs_inode_extref_name_len(eb, extref);

			cur_offset += sizeof(*extref);

		}

		btrfs_tree_read_unlock_blocking(eb);