[PATCH 4.19 297/346] ext4: fix a memory leak of ext4_free_data

From: Chunguang Xu <redacted>

commit cca415537244f6102cbb09b5b90db6ae2c953bdd upstream.

When freeing metadata, we will create an ext4_free_data and
insert it into the pending free list.  After the current
transaction is committed, the object will be freed.

ext4_mb_free_metadata() will check whether the area to be freed
overlaps with the pending free list. If true, return directly. At this
time, ext4_free_data is leaked.  Fortunately, the probability of this
problem is small, since it only occurs if the file system is corrupted
such that a block is claimed by more one inode and those inodes are
deleted within a single jbd2 transaction.

Signed-off-by: Chunguang Xu <redacted>
Link: https://lore.kernel.org/r/1604764698-4269-8-git-send-email-brookxu@tencent.com (local)
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ext4/mballoc.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c

@@ -4690,6 +4690,7 @@ ext4_mb_free_metadata(handle_t *handle,
 				ext4_group_first_block_no(sb, group) +
 				EXT4_C2B(sbi, cluster),
 				"Block already on to-be-freed list");
+			kmem_cache_free(ext4_free_data_cachep, new_entry);
 			return 0;
 		}
 	}