releases/4.16.4/ext4-protect-i_disksize-update-by-i_data_sem-in-direct-write-path.patch

   1 From 73fdad00b208b139cf43f3163fbc0f67e4c6047c Mon Sep 17 00:00:00 2001
   2 From: Eryu Guan <guaneryu@gmail.com>
   3 Date: Thu, 22 Mar 2018 11:41:25 -0400
   4 Subject: ext4: protect i_disksize update by i_data_sem in direct write path
   5
   6 From: Eryu Guan <guaneryu@gmail.com>
   7
   8 commit 73fdad00b208b139cf43f3163fbc0f67e4c6047c upstream.
   9
  10 i_disksize update should be protected by i_data_sem, by either taking
  11 the lock explicitly or by using ext4_update_i_disksize() helper. But the
  12 i_disksize updates in ext4_direct_IO_write() are not protected at all,
  13 which may be racing with i_disksize updates in writeback path in
  14 delalloc buffer write path.
  15
  16 This is found by code inspection, and I didn't hit any i_disksize
  17 corruption due to this bug. Thanks to Jan Kara for catching this bug and
  18 suggesting the fix!
  19
  20 Reported-by: Jan Kara <jack@suse.cz>
  21 Suggested-by: Jan Kara <jack@suse.cz>
  22 Signed-off-by: Eryu Guan <guaneryu@gmail.com>
  23 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  24 Cc: stable@vger.kernel.org
  25 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  26
  27 ---
  28  fs/ext4/inode.c |    5 ++---
  29  1 file changed, 2 insertions(+), 3 deletions(-)
  30
  31 --- a/fs/ext4/inode.c
  32 +++ b/fs/ext4/inode.c
  33 @@ -3658,7 +3658,6 @@ static ssize_t ext4_direct_IO_write(stru
  34  {
  35         struct file *file = iocb->ki_filp;
  36         struct inode *inode = file->f_mapping->host;
  37 -       struct ext4_inode_info *ei = EXT4_I(inode);
  38         ssize_t ret;
  39         loff_t offset = iocb->ki_pos;
  40         size_t count = iov_iter_count(iter);
  41 @@ -3682,7 +3681,7 @@ static ssize_t ext4_direct_IO_write(stru
  42                         goto out;
  43                 }
  44                 orphan = 1;
  45 -               ei->i_disksize = inode->i_size;
  46 +               ext4_update_i_disksize(inode, inode->i_size);
  47                 ext4_journal_stop(handle);
  48         }
  49
  50 @@ -3790,7 +3789,7 @@ static ssize_t ext4_direct_IO_write(stru
  51                 if (ret > 0) {
  52                         loff_t end = offset + ret;
  53                         if (end > inode->i_size) {
  54 -                               ei->i_disksize = end;
  55 +                               ext4_update_i_disksize(inode, end);
  56                                 i_size_write(inode, end);
  57                                 /*
  58                                  * We're going to return a positive `ret'