Re: [PATCH 4.4 1/2] ext4: fix crashes in dioread_nolock mode

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Sun, Apr 22, 2018 at 01:11:31AM -0700, Nathan Chancellor wrote:
> From: Jan Kara <jack@suse.cz>
> 
> commit 74dae4278546b897eb81784fdfcce872ddd8b2b8 upstream.
> 
> Competing overwrite DIO in dioread_nolock mode will just overwrite
> pointer to io_end in the inode. This may result in data corruption or
> extent conversion happening from IO completion interrupt because we
> don't properly set buffer_defer_completion() when unlocked DIO races
> with locked DIO to unwritten extent.
> 
> Since unlocked DIO doesn't need io_end for anything, just avoid
> allocating it and corrupting pointer from inode for locked DIO.
> A cleaner fix would be to avoid these games with io_end pointer from the
> inode but that requires more intrusive changes so we leave that for
> later.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
>  fs/ext4/inode.c | 40 ++++++++++++++++++++--------------------
>  1 file changed, 20 insertions(+), 20 deletions(-)
> 

Both patches now queued up, thanks!

greg k-h