[PATCH] cpuidle: dt: refactor deprecated strncpy

[PATCH] cpuidle: dt: refactor deprecated strncpy

[Justin Stitt]

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

We should prefer more robust and less ambiguous string interfaces.

A suitable replacement is `strscpy` [2] due to the fact that it guarantees
NUL-termination on the destination buffer. With this, we can also drop
the now unnecessary `CPUIDLE_(NAME|DESC)_LEN - 1` pieces.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Note: build-tested only
---
 drivers/cpuidle/dt_idle_states.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/cpuidle/dt_idle_states.c b/drivers/cpuidle/dt_idle_states.c
index 12fec92a85fd..97feb7d8fb23 100644
--- a/drivers/cpuidle/dt_idle_states.c
+++ b/drivers/cpuidle/dt_idle_states.c
@@ -84,8 +84,8 @@ static int init_state_node(struct cpuidle_state *idle_state,
 	 *	replace with kstrdup and pointer assignment when name
 	 *	and desc become string pointers
 	 */
-	strncpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN - 1);
-	strncpy(idle_state->desc, desc, CPUIDLE_DESC_LEN - 1);
+	strscpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN);
+	strscpy(idle_state->desc, desc, CPUIDLE_DESC_LEN);
 	return 0;
 }
 

---
base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
change-id: 20230913-strncpy-drivers-cpuidle-dt_idle_states-c-c84ea03c1379

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

Re: [PATCH] cpuidle: dt: refactor deprecated strncpy

[Kees Cook]

On Wed, Sep 13, 2023 at 12:23:19AM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We should prefer more robust and less ambiguous string interfaces.
> 
> A suitable replacement is `strscpy` [2] due to the fact that it guarantees
> NUL-termination on the destination buffer. With this, we can also drop
> the now unnecessary `CPUIDLE_(NAME|DESC)_LEN - 1` pieces.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

A very regular strncpy/strscpy conversion. :)

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH] cpuidle: dt: refactor deprecated strncpy

[Kees Cook]

On Wed, 13 Sep 2023 00:23:19 +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We should prefer more robust and less ambiguous string interfaces.
> 
> A suitable replacement is `strscpy` [2] due to the fact that it guarantees
> NUL-termination on the destination buffer. With this, we can also drop
> the now unnecessary `CPUIDLE_(NAME|DESC)_LEN - 1` pieces.
> 
> [...]

Applied to for-next/hardening, thanks!

[1/1] cpuidle: dt: refactor deprecated strncpy
      https://git.kernel.org/kees/c/fd94c38f8441

Take care,

-- 
Kees Cook