btrfs: Introduce btrfs_is_name_len_valid to avoid reading beyond boundary

Introduce function btrfs_is_name_len_valid.

The function compares parameter @name_len with item boundary then
returns true if name_len is valid.

Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ s/btrfs_leaf_data/BTRFS_LEAF_DATA_OFFSET/ ]
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 15a77e6..d182ce7 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3042,6 +3042,8 @@ struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_fs_info *fs_info,
                                                 struct btrfs_path *path,
                                                 const char *name,
                                                 int name_len);
+bool btrfs_is_name_len_valid(struct extent_buffer *leaf, int slot,
+                            unsigned long start, u16 name_len);
 
 /* orphan.c */
 int btrfs_insert_orphan_item(struct btrfs_trans_handle *trans,

diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
index c24d615..5b6c6fb 100644 (file)
--- a/fs/btrfs/dir-item.c
+++ b/fs/btrfs/dir-item.c
@@ -484,3 +484,75 @@ int verify_dir_item(struct btrfs_fs_info *fs_info,
 
        return 0;
 }
+
+bool btrfs_is_name_len_valid(struct extent_buffer *leaf, int slot,
+                            unsigned long start, u16 name_len)
+{
+       struct btrfs_fs_info *fs_info = leaf->fs_info;
+       struct btrfs_key key;
+       u32 read_start;
+       u32 read_end;
+       u32 item_start;
+       u32 item_end;
+       u32 size;
+       bool ret = true;
+
+       ASSERT(start > BTRFS_LEAF_DATA_OFFSET);
+
+       read_start = start - BTRFS_LEAF_DATA_OFFSET;
+       read_end = read_start + name_len;
+       item_start = btrfs_item_offset_nr(leaf, slot);
+       item_end = btrfs_item_end_nr(leaf, slot);
+
+       btrfs_item_key_to_cpu(leaf, &key, slot);
+
+       switch (key.type) {
+       case BTRFS_DIR_ITEM_KEY:
+       case BTRFS_XATTR_ITEM_KEY:
+       case BTRFS_DIR_INDEX_KEY:
+               size = sizeof(struct btrfs_dir_item);
+               break;
+       case BTRFS_INODE_REF_KEY:
+               size = sizeof(struct btrfs_inode_ref);
+               break;
+       case BTRFS_INODE_EXTREF_KEY:
+               size = sizeof(struct btrfs_inode_extref);
+               break;
+       case BTRFS_ROOT_REF_KEY:
+       case BTRFS_ROOT_BACKREF_KEY:
+               size = sizeof(struct btrfs_root_ref);
+               break;
+       default:
+               ret = false;
+               goto out;
+       }
+
+       if (read_start < item_start) {
+               ret = false;
+               goto out;
+       }
+       if (read_end > item_end) {
+               ret = false;
+               goto out;
+       }
+
+       /* there shall be item(s) before name */
+       if (read_start - item_start < size) {
+               ret = false;
+               goto out;
+       }
+
+       /*
+        * This may be the last item in the slot
+        * Or same type item(s) is left between read_end and item_end
+        */
+       if (item_end != read_end && item_end - read_end < size) {
+               ret = false;
+               goto out;
+       }
+out:
+       if (!ret)
+               btrfs_crit(fs_info, "invalid dir item name len: %u",
+                          (unsigned int)name_len);
+       return ret;
+}