[PATCH 2/2] btrfs: tree-checker: check item_size for dev_item

[Su Yue <l@damenly.su>]

Check item size before accessing the device item to avoid out of bound
access.

Signed-off-by: Su Yue <l@damenly.su>
---
 fs/btrfs/tree-checker.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index 2978fc89c093..87fff4345977 100644
--- 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;
+	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,
-- 
2.34.1