Btrfs: check btree node's nritems

When btree node (level = 1) has nritems which equals to zero,
we can end up with panic due to insert_ptr()'s

BUG_ON(slot > nritems);

where slot is 1 and nritems is 0, as copy_for_split() calls
insert_ptr(.., path->slots[1] + 1, ...);

A invalid value results in the whole mess, this adds the check
for btree's node nritems so that we stop reading block when
when something is wrong.

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>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index edda47162752..474209f50844 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -613,6 +613,19 @@ static noinline int check_leaf(struct btrfs_root *root,
         return 0;
 }
 
+static int check_node(struct btrfs_root *root, struct extent_buffer *node)
+{
+        unsigned long nr = btrfs_header_nritems(node);
+
+        if (nr == 0 || nr > BTRFS_NODEPTRS_PER_BLOCK(root)) {
+                btrfs_crit(root->fs_info,
+                           "corrupt node: block %llu root %llu nritems %lu",
+                           node->start, root->objectid, nr);
+                return -EIO;
+        }
+        return 0;
+}
+
 static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
                                       u64 phy_offset, struct page *page,
                                       u64 start, u64 end, int mirror)
@@ -683,6 +696,9 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
                 ret = -EIO;
         }
 
+        if (found_level > 0 && check_node(root, eb))
+                ret = -EIO;
+
         if (!ret)
                 set_extent_buffer_uptodate(eb);
 err: