[PATCH] Btrfs: error out if generic_bin_search get invalid arguments

[Liu Bo <bo.li.liu@oracle.com>]

With btrfs-corrupt-block, one can set btree node/leaf's field, if
we assign a negative value to node/leaf, we can get various hangs,
eg. if extent_root's nritems is -2ULL, then we get stuck in
 btrfs_read_block_groups() because it has a while loop and
btrfs_search_slot() on extent_root will always return the first
 child.

This lets us know what's happening and returns a EINVAL to callers
instead of returning the first item.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
 fs/btrfs/ctree.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index c49a500..915d224 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1770,6 +1770,14 @@ static noinline int generic_bin_search(struct extent_buffer *eb,
 	unsigned long map_len = 0;
 	int err;
 
+	if (low > high) {
+		btrfs_err(eb->fs_info,
+		 "%s: low (%d) < high (%d) eb %llu owner %llu level %d",
+			  __func__, low, high, eb->start,
+			  btrfs_header_owner(eb), btrfs_header_level(eb));
+		return -EINVAL;
+	}
+
 	while (low < high) {
 		mid = (low + high) / 2;
 		offset = p + mid * item_size;
-- 
2.5.5