Commit d4f76107 authored Nov 25, 2014 by Jan Kara Committed by Theodore Ts'o Nov 25, 2014

ext4: forbid journal_async_commit in data=ordered mode



Option journal_async_commit breaks gurantees of data=ordered mode as it
sends only a single cache flush after writing a transaction commit
block. Thus even though the transaction including the commit block is
fully stored on persistent storage, file data may still linger in drives
caches and will be lost on power failure. Since all checksums match on
journal recovery, we replay the transaction thus possibly exposing stale
user data.

To fix this data exposure issue, remove the possibility to use
journal_async_commit in data=ordered mode.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

parent d9f39d1e

fs/ext4/super.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -1695,6 +1695,12 @@ static int parse_options(char options, struct super_block sb,
		return 0;
		}
		}
		if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_ORDERED_DATA &&
		test_opt(sb, JOURNAL_ASYNC_COMMIT)) {
		ext4_msg(sb, KERN_ERR, "can't mount with journal_async_commit "
		"in data=ordered mode");
		return 0;
		}
		return 1;
		}

Admin message