linux-ext4 - Re: [PATCH v2] ext4: fix bug for rename with RENAME

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Message-ID: <20210104141953.GF4018@quack2.suse.cz>
Date:   Mon, 4 Jan 2021 15:19:53 +0100
From:   Jan Kara <jack@...e.cz>
To:     yangerkun <yangerkun@...wei.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jack@...e.cz, yi.zhang@...wei.com,
        lihaotian9@...wei.com, lutianxiong@...wei.com,
        linfeilong@...wei.com
Subject: Re: [PATCH v2] ext4: fix bug for rename with RENAME_WHITEOUT

On Tue 29-12-20 17:02:08, yangerkun wrote:
> ext4_rename will create a special inode for whiteout and use this 'ino'
> to replace the source file's dir entry 'ino'. Once error happens
> latter(small ext4 img, and consume all space, so the rename with dst
> path not exist will fail due to the ENOSPC return from ext4_add_entry in
> ext4_rename), the cleanup do drop the nlink for whiteout, but forget to
> restore 'ino' with source file. This will lead to "deleted inode
> referenced".
> 
> Signed-off-by: yangerkun <yangerkun@...wei.com>

Thanks for the patch! It looks mostly good, just one comment below:

>  end_rename:
> -	brelse(old.dir_bh);
> -	brelse(old.bh);
> -	brelse(new.bh);
>  	if (whiteout) {
> +		ext4_setent(handle, &old,
> +			    old.inode->i_ino, old_file_type);

I'm wondering here - how is it correct to reset the 'old' entry whenever
whiteout != NULL? I'd expect this to be guarded by the if (retval) check...

									Honza

>  		if (retval)
>  			drop_nlink(whiteout);
>  		unlock_new_inode(whiteout);
>  		iput(whiteout);
>  	}
> +	brelse(old.dir_bh);
> +	brelse(old.bh);
> +	brelse(new.bh);
>  	if (handle)
>  		ext4_journal_stop(handle);
>  	return retval;
> -- 
> 2.25.4
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR