linux-kernel - Re: [PATCH] kdb: Replace deprecated strcpy() with strscpy()

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Message-ID: <2025081408-swinging-endorphin-abe2@gregkh>
Date: Thu, 14 Aug 2025 14:35:56 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Thorsten Blum <thorsten.blum@...ux.dev>
Cc: Jason Wessel <jason.wessel@...driver.com>,
	Daniel Thompson <danielt@...nel.org>,
	Douglas Anderson <dianders@...omium.org>,
	Nir Lichtman <nir@...htman.org>,
	Yuran Pereira <yuran.pereira@...mail.com>,
	linux-hardening@...r.kernel.org,
	Daniel Thompson <daniel@...cstar.com>,
	kgdb-bugreport@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kdb: Replace deprecated strcpy() with strscpy()

On Thu, Aug 14, 2025 at 02:03:37PM +0200, Thorsten Blum wrote:
> strcpy() is deprecated; use strscpy() instead and remove several manual
> NUL-terminations.

Manual NULL terminations are good, why get rid of that?

> Since the destination buffers 'cmd_cur' and 'cmd_hist[cmd_head]' have
> the fixed length CMD_BUFLEN, strscpy() automatically determines their
> size using sizeof() when the size argument is omitted. This makes the
> explicit size arguments for the existing strscpy() calls unnecessary,
> remove them.

But now you are dynamically calculating this?

> No functional changes intended.

How did you test this?  Many of these types of changes are wrong, so you
really really need to prove it is correct.

> 
> Link: https://github.com/KSPP/linux/issues/88
> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
> ---
>  kernel/debug/kdb/kdb_main.c | 32 ++++++++++++++------------------
>  1 file changed, 14 insertions(+), 18 deletions(-)
> 
> diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
> index 7a4d2d4689a5..ea7dc2540e40 100644
> --- a/kernel/debug/kdb/kdb_main.c
> +++ b/kernel/debug/kdb/kdb_main.c
> @@ -727,14 +727,10 @@ static int kdb_defcmd(int argc, const char **argv)
>  	mp->help = kdb_strdup(argv[3], GFP_KDB);
>  	if (!mp->help)
>  		goto fail_help;
> -	if (mp->usage[0] == '"') {
> -		strcpy(mp->usage, argv[2]+1);
> -		mp->usage[strlen(mp->usage)-1] = '\0';
> -	}
> -	if (mp->help[0] == '"') {
> -		strcpy(mp->help, argv[3]+1);
> -		mp->help[strlen(mp->help)-1] = '\0';
> -	}
> +	if (mp->usage[0] == '"')
> +		strscpy(mp->usage, argv[2] + 1, strlen(argv[2]) - 1);

Now you are manually testing the length of argv[2], are you sure that's
ok?

> +	if (mp->help[0] == '"')
> +		strscpy(mp->help, argv[3] + 1, strlen(argv[3]) - 1);
>  
>  	INIT_LIST_HEAD(&kdb_macro->statements);
>  	defcmd_in_progress = true;
> @@ -860,7 +856,7 @@ static void parse_grep(const char *str)
>  		kdb_printf("search string too long\n");
>  		return;
>  	}
> -	strcpy(kdb_grep_string, cp);
> +	strscpy(kdb_grep_string, cp);

If this was just a search/replace, it would have been done already, so
why is this ok?


>  	kdb_grepping_flag++;
>  	return;
>  }
> @@ -1076,12 +1072,12 @@ static int handle_ctrl_cmd(char *cmd)
>  		if (cmdptr != cmd_tail)
>  			cmdptr = (cmdptr + KDB_CMD_HISTORY_COUNT - 1) %
>  				 KDB_CMD_HISTORY_COUNT;
> -		strscpy(cmd_cur, cmd_hist[cmdptr], CMD_BUFLEN);
> +		strscpy(cmd_cur, cmd_hist[cmdptr]);

Same here.  And other places...

thanks,

greg k-h