Btrfs: error out if generic_bin_search get invalid arguments

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>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index a85cf7d2330981d606352cc8218167570db5507a..362879da4f0d2f09c6553f827e0898f6088e1d6f 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1771,6 +1771,14 @@ 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;