[PATCH v2] platform/x86: think-lmi: Fix current password length check

[PATCH v2] platform/x86: think-lmi: Fix current password length check

[Thorsten Blum]

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: stable@vger.kernel.org
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
Changes in v2:
- Keep and reword the newline comment
- v1: https://lore.kernel.org/r/20260810132018.156868-3-thorsten.blum@linux.dev/
---
 drivers/platform/x86/lenovo/think-lmi.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/x86/lenovo/think-lmi.c b/drivers/platform/x86/lenovo/think-lmi.c
index e215e86e3db7..d0ceb6aaa69e 100644
--- a/drivers/platform/x86/lenovo/think-lmi.c
+++ b/drivers/platform/x86/lenovo/think-lmi.c
@@ -438,14 +438,14 @@ static ssize_t current_password_store(struct kobject *kobj,
 	struct tlmi_pwd_setting *setting = to_tlmi_pwd_setting(kobj);
 	size_t pwdlen;
 
-	pwdlen = strlen(buf);
+	/* Strip newline; setting password won't work if one is present. */
+	pwdlen = strchrnul(buf, '\n') - 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;
 }
 

Re: [PATCH v2] platform/x86: think-lmi: Fix current password length check

[Mark Pearson]

Thanks Thorsten

On Thu, Aug 13, 2026, at 4:20 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: stable@vger.kernel.org
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
> Changes in v2:
> - Keep and reword the newline comment
> - v1: 
> https://lore.kernel.org/r/20260810132018.156868-3-thorsten.blum@linux.dev/
> ---
>  drivers/platform/x86/lenovo/think-lmi.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/platform/x86/lenovo/think-lmi.c 
> b/drivers/platform/x86/lenovo/think-lmi.c
> index e215e86e3db7..d0ceb6aaa69e 100644
> --- a/drivers/platform/x86/lenovo/think-lmi.c
> +++ b/drivers/platform/x86/lenovo/think-lmi.c
> @@ -438,14 +438,14 @@ static ssize_t current_password_store(struct 
> kobject *kobj,
>  	struct tlmi_pwd_setting *setting = to_tlmi_pwd_setting(kobj);
>  	size_t pwdlen;
> 
> -	pwdlen = strlen(buf);
> +	/* Strip newline; setting password won't work if one is present. */
> +	pwdlen = strchrnul(buf, '\n') - 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;
>  }

Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Mark