Btrfs: add checks to verify dir items are correct

We need to make sure the dir items we get are valid dir items.  So any time we
try and read one check it with verify_dir_item, which will do various sanity
checks to make sure it looks sane.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
index f0cad5ae5be7..02c97ad61b6d 100644
--- a/fs/btrfs/dir-item.c
+++ b/fs/btrfs/dir-item.c
@@ -377,6 +377,9 @@ struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_root *root,
 
         leaf = path->nodes[0];
         dir_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dir_item);
+        if (verify_dir_item(root, leaf, dir_item))
+                return NULL;
+
         total_len = btrfs_item_size_nr(leaf, path->slots[0]);
         while (cur < total_len) {
                 this_len = sizeof(*dir_item) +
@@ -429,3 +432,35 @@ int btrfs_delete_one_dir_name(struct btrfs_trans_handle *trans,
         }
         return ret;
 }
+
+int verify_dir_item(struct btrfs_root *root,
+                    struct extent_buffer *leaf,
+                    struct btrfs_dir_item *dir_item)
+{
+        u16 namelen = BTRFS_NAME_LEN;
+        u8 type = btrfs_dir_type(leaf, dir_item);
+
+        if (type >= BTRFS_FT_MAX) {
+                printk(KERN_CRIT "btrfs: invalid dir item type: %d\n",
+                       (int)type);
+                return 1;
+        }
+
+        if (type == BTRFS_FT_XATTR)
+                namelen = XATTR_NAME_MAX;
+
+        if (btrfs_dir_name_len(leaf, dir_item) > namelen) {
+                printk(KERN_CRIT "btrfS: invalid dir item name len: %u\n",
+                       (unsigned)btrfs_dir_data_len(leaf, dir_item));
+                return 1;
+        }
+
+        /* BTRFS_MAX_XATTR_SIZE is the same for all dir items */
+        if (btrfs_dir_data_len(leaf, dir_item) > BTRFS_MAX_XATTR_SIZE(root)) {
+                printk(KERN_CRIT "btrfs: invalid dir item data len: %u\n",
+                       (unsigned)btrfs_dir_data_len(leaf, dir_item));
+                return 1;
+        }
+
+        return 0;
+}