linux-kernel - Re: [PATCH v1 1/3] jbd2: Avoid printing out the boundary

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Message-ID: <20230323095346.ibpv25xjjf6rozpv@quack3>
Date:   Thu, 23 Mar 2023 10:53:46 +0100
From:   Jan Kara <jack@...e.cz>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        Theodore Ts'o <tytso@....edu>, Jan Kara <jack@...e.com>,
        Andy Shevchenko <andy@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v1 1/3] jbd2: Avoid printing out the boundary

On Wed 22-03-23 16:12:04, Andy Shevchenko wrote:
> Theoretically possible that "%pg" will take all room for the j_devname
> and hence the "-%lu" will go out the boundary due to unconditional
> sprintf() in use. To make this code more robust, replace two sequential
> s*printf():s by a single call and then replace forbidden character.
> It's possible to do this way, because '/' won't ever be in the result
> of "-%lu".
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Looks good. Feel free to add:

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

								Honza

> ---
>  fs/jbd2/journal.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 8ae419152ff6..00c0aa4a3a91 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -1515,9 +1515,8 @@ journal_t *jbd2_journal_init_inode(struct inode *inode)
>  
>  	journal->j_inode = inode;
>  	snprintf(journal->j_devname, sizeof(journal->j_devname),
> -		 "%pg", journal->j_dev);
> -	p = strreplace(journal->j_devname, '/', '!');
> -	sprintf(p, "-%lu", journal->j_inode->i_ino);
> +		 "%pg-%lu", journal->j_dev, journal->j_inode->i_ino);
> +	strreplace(journal->j_devname, '/', '!');
>  	jbd2_stats_proc_init(journal);
>  
>  	return journal;
> -- 
> 2.40.0.1.gaa8946217a0b
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR