linux-ext4 - Re: [PATCH 1/4] ext4: Fix possible use-after-free with AIO

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Date:	Wed, 23 Jan 2013 08:18:10 -0500
From:	Carlos Maiolino <cmaiolino@...hat.com>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-fsdevel@...r.kernel.org, tytso@....edu, bpm@....com,
	jlbec@...lplan.org, linux-ext4@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH 1/4] ext4: Fix possible use-after-free with AIO

Looks Good,

Reviewed-by: Carlos Maiolino <cmaiolino@...hat.com>
On Wed, Jan 23, 2013 at 01:56:17PM +0100, Jan Kara wrote:
> Running AIO is pinning inode in memory using file reference. Once AIO
> is completed using aio_complete(), file reference is put and inode can
> be freed from memory. So we have to be sure that calling aio_complete()
> is the last thing we do with the inode.
> 
> CC: linux-ext4@...r.kernel.org
> CC: "Theodore Ts'o" <tytso@....edu>
> CC: stable@...r.kernel.org
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext4/inode.c   |    2 +-
>  fs/ext4/page-io.c |    9 ++++-----
>  2 files changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index cbfe13b..ba06638 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2977,9 +2977,9 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
>  	if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
>  		ext4_free_io_end(io_end);
>  out:
> +		inode_dio_done(inode);
>  		if (is_async)
>  			aio_complete(iocb, ret, 0);
> -		inode_dio_done(inode);
>  		return;
>  	}
>  
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 0016fbc..b42d04f 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -103,14 +103,13 @@ static int ext4_end_io(ext4_io_end_t *io)
>  			 "(inode %lu, offset %llu, size %zd, error %d)",
>  			 inode->i_ino, offset, size, ret);
>  	}
> -	if (io->iocb)
> -		aio_complete(io->iocb, io->result, 0);
> -
> -	if (io->flag & EXT4_IO_END_DIRECT)
> -		inode_dio_done(inode);
>  	/* Wake up anyone waiting on unwritten extent conversion */
>  	if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
>  		wake_up_all(ext4_ioend_wq(inode));
> +	if (io->flag & EXT4_IO_END_DIRECT)
> +		inode_dio_done(inode);
> +	if (io->iocb)
> +		aio_complete(io->iocb, io->result, 0);
>  	return ret;
>  }
>  
> -- 
> 1.7.1
> 
> --
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-- 
Carlos
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