From d4f761074353b9aa42a3bdd039d78e1af5f5f29f Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 25 Nov 2014 20:19:17 -0500 Subject: [PATCH] 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 Signed-off-by: Theodore Ts'o --- fs/ext4/super.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index f8ad756bb852..4fca81cc8fce 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -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; }