diff mbox series

s390/ipl: refactor deprecated strncpy

Message ID 20230811-arch-s390-kernel-v1-1-7edbeeab3809@google.com
State New
Headers
Series s390/ipl: refactor deprecated strncpy |

Commit Message

Justin Stitt Aug. 11, 2023, 9:56 p.m. UTC 
  `strncpy` is deprecated for use on NUL-terminated destination strings [1].

Use `strscpy_pad` which has the same behavior as `strncpy` here with the
extra safeguard of guaranteeing NUL-termination of destination strings.
In it's current form, this may result in silent truncation if the src
string has the same size as the destination string.

Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
 arch/s390/kernel/ipl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


---
base-commit: 52a93d39b17dc7eb98b6aa3edb93943248e03b2f
change-id: 20230811-arch-s390-kernel-968d0545c45a

Best regards,
--
Justin Stitt <justinstitt@google.com>

Comments

Kees Cook Aug. 14, 2023, 11:32 p.m. UTC | #1 
On Fri, Aug 11, 2023 at 09:56:15PM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> Use `strscpy_pad` which has the same behavior as `strncpy` here with the
> extra safeguard of guaranteeing NUL-termination of destination strings.
> In it's current form, this may result in silent truncation if the src
> string has the same size as the destination string.
> 
> Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>
> ---
>  arch/s390/kernel/ipl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
> index 85a00d97a314..a6dcf6f28197 100644
> --- a/arch/s390/kernel/ipl.c
> +++ b/arch/s390/kernel/ipl.c
> @@ -266,7 +266,7 @@ static ssize_t sys_##_prefix##_##_name##_store(struct kobject *kobj,	\
>  		struct kobj_attribute *attr,				\
>  		const char *buf, size_t len)				\
>  {									\
> -	strncpy(_value, buf, sizeof(_value) - 1);			\
> +	strscpy_pad(_value, buf, sizeof(_value));			\

Padding isn't needed here -- the string are consumed by __cpcmd(), which
explicitly uses strlen() and a memcpy to pass them off.

>  	strim(_value);							\

This existing code line is buggy, though -- it will not trim leading
whitespace in the buffer. (It _returns_ a string that has been
forward-adjusted.)

I think this is an API mistake -- strim() should either do in-place
changes for both ends or be defined with __much_check so the return
value doesn't get lost. (But this is a separate issue.)

-Kees
diff mbox series

Patch

diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
index 85a00d97a314..a6dcf6f28197 100644
--- a/arch/s390/kernel/ipl.c
+++ b/arch/s390/kernel/ipl.c
@@ -266,7 +266,7 @@  static ssize_t sys_##_prefix##_##_name##_store(struct kobject *kobj,	\
 		struct kobj_attribute *attr,				\
 		const char *buf, size_t len)				\
 {									\
-	strncpy(_value, buf, sizeof(_value) - 1);			\
+	strscpy_pad(_value, buf, sizeof(_value));			\
 	strim(_value);							\
 	return len;							\
 }									\