From fa0897757db7e75dd60b63871249d9e34936f885 Mon Sep 17 00:00:00 2001 From: Lukas Czerner Date: Fri, 10 May 2019 21:45:33 -0400 Subject: [PATCH] ext4: fix data corruption caused by overlapping unaligned and aligned IO commit 57a0da28ced8707cb9f79f071a016b9d005caf5a upstream. Unaligned AIO must be serialized because the zeroing of partial blocks of unaligned AIO can result in data corruption in case it's overlapping another in flight IO. Currently we wait for all unwritten extents before we submit unaligned AIO which protects data in case of unaligned AIO is following overlapping IO. However if a unaligned AIO is followed by overlapping aligned AIO we can still end up corrupting data. To fix this, we must make sure that the unaligned AIO is the only IO in flight by waiting for unwritten extents conversion not just before the IO submission, but right after it as well. This problem can be reproduced by xfstest generic/538 Signed-off-by: Lukas Czerner Signed-off-by: Theodore Ts'o Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman --- fs/ext4/file.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index fe76d0957a1f..59d3ea7094a0 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -163,6 +163,13 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from) } ret = __generic_file_write_iter(iocb, from); + /* + * Unaligned direct AIO must be the only IO in flight. Otherwise + * overlapping aligned IO after unaligned might result in data + * corruption. + */ + if (ret == -EIOCBQUEUED && unaligned_aio) + ext4_unwritten_wait(inode); inode_unlock(inode); if (ret > 0) -- 2.20.1