Re: [PATCH] platform/x86: think-lmi: Fix current password length check

On Mon, Aug 10, 2026, at 9:20 AM, Thorsten Blum wrote:
> current_password_store() checks the password length before removing the
> trailing newline, which can reject valid passwords that are exactly
> ->maxlen bytes long.
>
> It also passes ->maxlen to strscpy(), which truncates passwords without
> a newline.
>
> Use strchrnul() to measure the password length up to the newline, then
> copy that many bytes and add a trailing NUL terminator.
>
> Fixes: a40cd7ef22fb ("platform/x86: think-lmi: Add WMI interface 
> support on Lenovo platforms")
> Cc: [email protected]
> Signed-off-by: Thorsten Blum <[email protected]>
> ---
>  drivers/platform/x86/lenovo/think-lmi.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/platform/x86/lenovo/think-lmi.c 
> b/drivers/platform/x86/lenovo/think-lmi.c
> index e215e86e3db7..860224dc8c21 100644
> --- a/drivers/platform/x86/lenovo/think-lmi.c
> +++ b/drivers/platform/x86/lenovo/think-lmi.c
> @@ -436,16 +436,14 @@ static ssize_t current_password_store(struct 
> kobject *kobj,
>  				      const char *buf, size_t count)
>  {
>  	struct tlmi_pwd_setting *setting = to_tlmi_pwd_setting(kobj);
> -	size_t pwdlen;
> +	size_t pwdlen = strchrnul(buf, '\n') - buf;
> 
> -	pwdlen = strlen(buf);
>  	/* pwdlen == 0 is allowed to clear the password */
>  	if (pwdlen && ((pwdlen < setting->minlen) || (pwdlen > setting->maxlen)))
>  		return -EINVAL;
> 
> -	strscpy(setting->password, buf, setting->maxlen);
> -	/* Strip out CR if one is present, setting password won't work if it 
> is present */
> -	strreplace(setting->password, '\n', '\0');
> +	memcpy(setting->password, buf, pwdlen);
> +	setting->password[pwdlen] = '\0';
>  	return count;
>  }

Change is good.
Only minor note is that I hate to lose the comment explaining why we're losing the CR. Can we put that back in above the strchrnul operation?

Mark