btrfs: ref-verify: fix memory leaks

In btrfs_ref_tree_mod(), 'ref' and 'ra' are allocated through kzalloc() and
kmalloc(), respectively. In the following code, if an error occurs, the
execution will be redirected to 'out' or 'out_unlock' and the function will
be exited. However, on some of the paths, 'ref' and 'ra' are not
deallocated, leading to memory leaks. For example, if 'action' is
BTRFS_ADD_DELAYED_EXTENT, add_block_entry() will be invoked. If the return
value indicates an error, the execution will be redirected to 'out'. But,
'ref' is not deallocated on this path, causing a memory leak.

To fix the above issues, deallocate both 'ref' and 'ra' before exiting from
the function when an error is encountered.

CC: stable@vger.kernel.org # 4.15+
Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ref-verify.c

@@ -744,6 +744,7 @@ int btrfs_ref_tree_mod(struct btrfs_fs_info *fs_info,
 		 */
 		be = add_block_entry(fs_info, bytenr, num_bytes, ref_root);
 		if (IS_ERR(be)) {
+			kfree(ref);
 			kfree(ra);
 			ret = PTR_ERR(be);
 			goto out;
@@ -757,6 +758,8 @@ int btrfs_ref_tree_mod(struct btrfs_fs_info *fs_info,
 			"re-allocated a block that still has references to it!");
 			dump_block_entry(fs_info, be);
 			dump_ref_action(fs_info, ra);
+			kfree(ref);
+			kfree(ra);
 			goto out_unlock;
 		}
 
@@ -819,6 +822,7 @@ int btrfs_ref_tree_mod(struct btrfs_fs_info *fs_info,
 "dropping a ref for a existing root that doesn't have a ref on the block");
 				dump_block_entry(fs_info, be);
 				dump_ref_action(fs_info, ra);
+				kfree(ref);
 				kfree(ra);
 				goto out_unlock;
 			}
@@ -834,6 +838,7 @@ int btrfs_ref_tree_mod(struct btrfs_fs_info *fs_info,
 "attempting to add another ref for an existing ref on a tree block");
 			dump_block_entry(fs_info, be);
 			dump_ref_action(fs_info, ra);
+			kfree(ref);
 			kfree(ra);
 			goto out_unlock;
 		}