drm/nouveau/pm: refactor deprecated strncpy

[PATCH] drm/nouveau/pm: refactor deprecated strncpy

Posted by Justin Stitt 2 years, 5 months ago

`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 without unnecessarily NUL-padding.

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>
---
 drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c b/drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c
index 8fe0444f761e..131db2645f84 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c
@@ -462,7 +462,7 @@ nvkm_perfmon_mthd_query_domain(struct nvkm_perfmon *perfmon,
 
 		args->v0.id         = di;
 		args->v0.signal_nr  = nvkm_perfdom_count_perfsig(dom);
-		strncpy(args->v0.name, dom->name, sizeof(args->v0.name) - 1);
+		strscpy(args->v0.name, dom->name, sizeof(args->v0.name));
 
 		/* Currently only global counters (PCOUNTER) are implemented
 		 * but this will be different for local counters (MP). */
@@ -513,8 +513,7 @@ nvkm_perfmon_mthd_query_signal(struct nvkm_perfmon *perfmon,
 			snprintf(args->v0.name, sizeof(args->v0.name),
 				 "/%s/%02x", dom->name, si);
 		} else {
-			strncpy(args->v0.name, sig->name,
-				sizeof(args->v0.name) - 1);
+			strscpy(args->v0.name, sig->name, sizeof(args->v0.name));
 		}
 
 		args->v0.signal = si;
@@ -572,7 +571,7 @@ nvkm_perfmon_mthd_query_source(struct nvkm_perfmon *perfmon,
 
 		args->v0.source = sig->source[si];
 		args->v0.mask   = src->mask;
-		strncpy(args->v0.name, src->name, sizeof(args->v0.name) - 1);
+		strscpy(args->v0.name, src->name, sizeof(args->v0.name));
 	}
 
 	if (++si < source_nr) {

---
base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
change-id: 20230914-strncpy-drivers-gpu-drm-nouveau-nvkm-engine-pm-base-c-38bf9c78bc0f

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

Re: [PATCH] drm/nouveau/pm: refactor deprecated strncpy

Posted by Lyude Paul 2 years, 4 months ago

...oops, responded to the wrong email :P

Reviewed-by: Lyude Paul <lyude@redhat.com>


On Thu, 2023-09-14 at 22:17 +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 without unnecessarily NUL-padding.
> 
> 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>
> ---
>  drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c b/drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c
> index 8fe0444f761e..131db2645f84 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/engine/pm/base.c
> @@ -462,7 +462,7 @@ nvkm_perfmon_mthd_query_domain(struct nvkm_perfmon *perfmon,
>  
>  		args->v0.id         = di;
>  		args->v0.signal_nr  = nvkm_perfdom_count_perfsig(dom);
> -		strncpy(args->v0.name, dom->name, sizeof(args->v0.name) - 1);
> +		strscpy(args->v0.name, dom->name, sizeof(args->v0.name));
>  
>  		/* Currently only global counters (PCOUNTER) are implemented
>  		 * but this will be different for local counters (MP). */
> @@ -513,8 +513,7 @@ nvkm_perfmon_mthd_query_signal(struct nvkm_perfmon *perfmon,
>  			snprintf(args->v0.name, sizeof(args->v0.name),
>  				 "/%s/%02x", dom->name, si);
>  		} else {
> -			strncpy(args->v0.name, sig->name,
> -				sizeof(args->v0.name) - 1);
> +			strscpy(args->v0.name, sig->name, sizeof(args->v0.name));
>  		}
>  
>  		args->v0.signal = si;
> @@ -572,7 +571,7 @@ nvkm_perfmon_mthd_query_source(struct nvkm_perfmon *perfmon,
>  
>  		args->v0.source = sig->source[si];
>  		args->v0.mask   = src->mask;
> -		strncpy(args->v0.name, src->name, sizeof(args->v0.name) - 1);
> +		strscpy(args->v0.name, src->name, sizeof(args->v0.name));
>  	}
>  
>  	if (++si < source_nr) {
> 
> ---
> base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
> change-id: 20230914-strncpy-drivers-gpu-drm-nouveau-nvkm-engine-pm-base-c-38bf9c78bc0f
> 
> Best regards,
> --
> Justin Stitt <justinstitt@google.com>
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat

Re: [PATCH] drm/nouveau/pm: refactor deprecated strncpy

Posted by Kees Cook 2 years, 4 months ago

On Thu, Sep 14, 2023 at 10:17:08PM +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 without unnecessarily NUL-padding.
> 
> 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>

The "- 1" use in the original code is strong evidence for this being a
sane conversion. :)

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

-- 
Kees Cook

Re: [PATCH] drm/nouveau/pm: refactor deprecated strncpy

Posted by Lyude Paul 2 years, 4 months ago

Nice catch!

Reviewed-by: Lyude Paul <lyude@redhat.com>

Will push in just a moment

On Thu, 2023-09-14 at 21:59 -0700, Kees Cook wrote:
> On Thu, Sep 14, 2023 at 10:17:08PM +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 without unnecessarily NUL-padding.
> > 
> > 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>
> 
> The "- 1" use in the original code is strong evidence for this being a
> sane conversion. :)
> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat