queue-4.19/ext4-fix-data-corruption-caused-by-overlapping-unaligned-and-aligned-io.patch

   1 From 57a0da28ced8707cb9f79f071a016b9d005caf5a Mon Sep 17 00:00:00 2001
   2 From: Lukas Czerner <lczerner@redhat.com>
   3 Date: Fri, 10 May 2019 21:45:33 -0400
   4 Subject: ext4: fix data corruption caused by overlapping unaligned and aligned IO
   5
   6 From: Lukas Czerner <lczerner@redhat.com>
   7
   8 commit 57a0da28ced8707cb9f79f071a016b9d005caf5a upstream.
   9
  10 Unaligned AIO must be serialized because the zeroing of partial blocks
  11 of unaligned AIO can result in data corruption in case it's overlapping
  12 another in flight IO.
  13
  14 Currently we wait for all unwritten extents before we submit unaligned
  15 AIO which protects data in case of unaligned AIO is following overlapping
  16 IO. However if a unaligned AIO is followed by overlapping aligned AIO we
  17 can still end up corrupting data.
  18
  19 To fix this, we must make sure that the unaligned AIO is the only IO in
  20 flight by waiting for unwritten extents conversion not just before the
  21 IO submission, but right after it as well.
  22
  23 This problem can be reproduced by xfstest generic/538
  24
  25 Signed-off-by: Lukas Czerner <lczerner@redhat.com>
  26 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  27 Cc: stable@kernel.org
  28 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  29
  30 ---
  31  fs/ext4/file.c |    7 +++++++
  32  1 file changed, 7 insertions(+)
  33
  34 --- a/fs/ext4/file.c
  35 +++ b/fs/ext4/file.c
  36 @@ -264,6 +264,13 @@ ext4_file_write_iter(struct kiocb *iocb,
  37         }
  38
  39         ret = __generic_file_write_iter(iocb, from);
  40 +       /*
  41 +        * Unaligned direct AIO must be the only IO in flight. Otherwise
  42 +        * overlapping aligned IO after unaligned might result in data
  43 +        * corruption.
  44 +        */
  45 +       if (ret == -EIOCBQUEUED && unaligned_aio)
  46 +               ext4_unwritten_wait(inode);
  47         inode_unlock(inode);
  48
  49         if (ret > 0)