btrfs: tree-checker: check item_size for dev_item

Check item size before accessing the device item to avoid out of bound
access, similar to inode_item check.

Signed-off-by: Su Yue <l@damenly.su>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index a819eb5..9fd145f 100644 (file)
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -965,6 +965,7 @@ static int check_dev_item(struct extent_buffer *leaf,
                          struct btrfs_key *key, int slot)
 {
        struct btrfs_dev_item *ditem;
+       const u32 item_size = btrfs_item_size(leaf, slot);
 
        if (unlikely(key->objectid != BTRFS_DEV_ITEMS_OBJECTID)) {
                dev_item_err(leaf, slot,
@@ -972,6 +973,13 @@ static int check_dev_item(struct extent_buffer *leaf,
                             key->objectid, BTRFS_DEV_ITEMS_OBJECTID);
                return -EUCLEAN;
        }
+
+       if (unlikely(item_size != sizeof(*ditem))) {
+               dev_item_err(leaf, slot, "invalid item size: has %u expect %zu",
+                            item_size, sizeof(*ditem));
+               return -EUCLEAN;
+       }
+
        ditem = btrfs_item_ptr(leaf, slot, struct btrfs_dev_item);
        if (unlikely(btrfs_device_id(leaf, ditem) != key->offset)) {
                dev_item_err(leaf, slot,