linux-ext4 - Re: [PATCH v2 1/2] ext4: protect i_disksize update by i_data

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 23 Mar 2018 18:00:26 +0100
From:   Jan Kara <jack@...e.cz>
To:     Eryu Guan <guaneryu@...il.com>
Cc:     linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
        Jan Kara <jack@...e.cz>
Subject: Re: [PATCH v2 1/2] ext4: protect i_disksize update by i_data_sem in
 direct write path

On Mon 12-03-18 23:21:55, Eryu Guan wrote:
> i_disksize update should be protected by i_data_sem, by either taking
> the lock explicitly or by using ext4_update_i_disksize() helper. But the
> i_disksize updates in ext4_direct_IO_write() are not protected at all,
> which may be racing with i_disksize updates in writeback path in
> delalloc buffer write path.
> 
> This is found by code inspection, and I didn't hit any i_disksize
> corruption due to this bug. Thanks to Jan Kara for catching this bug and
> suggesting the fix!
> 
> Reported-by: Jan Kara <jack@...e.cz>
> Suggested-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Eryu Guan <guaneryu@...il.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza


> ---
> 
> There's no v1 version of this patch.
> 
> It's a bit unfortunate that I have to remove the "ei" definition in this
> patch and reintroduce it in patch 2/2, otherwise I got transient
> "defined but not used" build warning with only this patch applied.
> 
>  fs/ext4/inode.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index c94780075b04..bff44b4a0783 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3658,7 +3658,6 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
>  {
>  	struct file *file = iocb->ki_filp;
>  	struct inode *inode = file->f_mapping->host;
> -	struct ext4_inode_info *ei = EXT4_I(inode);
>  	ssize_t ret;
>  	loff_t offset = iocb->ki_pos;
>  	size_t count = iov_iter_count(iter);
> @@ -3682,7 +3681,7 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
>  			goto out;
>  		}
>  		orphan = 1;
> -		ei->i_disksize = inode->i_size;
> +		ext4_update_i_disksize(inode, inode->i_size);
>  		ext4_journal_stop(handle);
>  	}
>  
> @@ -3790,7 +3789,7 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
>  		if (ret > 0) {
>  			loff_t end = offset + ret;
>  			if (end > inode->i_size) {
> -				ei->i_disksize = end;
> +				ext4_update_i_disksize(inode, end);
>  				i_size_write(inode, end);
>  				/*
>  				 * We're going to return a positive `ret'
> -- 
> 2.14.3
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR