linux-kernel - Re: [PATCH v3] kconfig/lxdialog: replace strcpy() with strncpy() in inputbox.c

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Message-ID: <2025072842-require-smokeless-f98f@gregkh>
Date: Mon, 28 Jul 2025 06:29:12 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Suchit Karunakaran <suchitkarunakaran@...il.com>
Cc: masahiroy@...nel.org, nicolas.schier@...ux.dev,
	linux-kbuild@...r.kernel.org, skhan@...uxfoundation.org,
	linux-kernel-mentees@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] kconfig/lxdialog: replace strcpy() with strncpy() in
 inputbox.c

On Sun, Jul 27, 2025 at 10:14:33PM +0530, Suchit Karunakaran wrote:
> strcpy() performs no bounds checking and can lead to buffer overflows if
> the input string exceeds the destination buffer size. This patch replaces
> it with strncpy(), and null terminates the input string.
> 
> Signed-off-by: Suchit Karunakaran <suchitkarunakaran@...il.com>
> ---
>  scripts/kconfig/lxdialog/inputbox.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/kconfig/lxdialog/inputbox.c b/scripts/kconfig/lxdialog/inputbox.c
> index 3c6e24b20f5b..5e4a131724f2 100644
> --- a/scripts/kconfig/lxdialog/inputbox.c
> +++ b/scripts/kconfig/lxdialog/inputbox.c
> @@ -39,8 +39,10 @@ int dialog_inputbox(const char *title, const char *prompt, int height, int width
>  
>  	if (!init)
>  		instr[0] = '\0';
> -	else
> -		strcpy(instr, init);
> +	else {
> +		strncpy(instr, init, sizeof(dialog_input_result) - 1);
> +		instr[sizeof(dialog_input_result) - 1] = '\0';

As this is a userspace tool, why is this change needed at all?  How can
this overflow and if it does, what happens?

thanks,

greg k-h