`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.
There is likely no bug in the current implementation due to the safeguard:
| cname[sizeof(cname) - 1] = '\0';
... however we can provide simpler and easier to understand code using
the newer (and recommended) `strscpy` api.
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: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
drivers/gpu/drm/nouveau/nvkm/core/firmware.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
index 91fb494d4009..374212da9e95 100644
--- a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
+++ b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
@@ -79,8 +79,7 @@ nvkm_firmware_get(const struct nvkm_subdev *subdev, const char *fwname, int ver,
int i;
/* Convert device name to lowercase */
- strncpy(cname, device->chip->name, sizeof(cname));
- cname[sizeof(cname) - 1] = '\0';
+ strscpy(cname, device->chip->name, sizeof(cname));
i = strlen(cname);
while (i) {
--i;
---
base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
change-id: 20230914-strncpy-drivers-gpu-drm-nouveau-nvkm-core-firmware-c-791223838b72
Best regards,
--
Justin Stitt <[email protected]>
On Thu, Sep 14, 2023 at 09:40:49PM +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.
>
> There is likely no bug in the current implementation due to the safeguard:
> | cname[sizeof(cname) - 1] = '\0';
> ... however we can provide simpler and easier to understand code using
> the newer (and recommended) `strscpy` api.
>
> 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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
> ---
> drivers/gpu/drm/nouveau/nvkm/core/firmware.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
> index 91fb494d4009..374212da9e95 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
> @@ -79,8 +79,7 @@ nvkm_firmware_get(const struct nvkm_subdev *subdev, const char *fwname, int ver,
> int i;
>
> /* Convert device name to lowercase */
> - strncpy(cname, device->chip->name, sizeof(cname));
> - cname[sizeof(cname) - 1] = '\0';
> + strscpy(cname, device->chip->name, sizeof(cname));
> i = strlen(cname);
> while (i) {
> --i;
Yup, consumed by strlen() and snprintf(). Looks like a standard
conversion. :)
Reviewed-by: Kees Cook <[email protected]>
-Kees
>
> ---
> base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
> change-id: 20230914-strncpy-drivers-gpu-drm-nouveau-nvkm-core-firmware-c-791223838b72
>
> Best regards,
> --
> Justin Stitt <[email protected]>
>
--
Kees Cook
Eek, I didn't realize how many instances of this we had. Thanks for doing this
:)
Reviewed-by: Lyude Paul <[email protected]>
On Thu, 2023-09-14 at 21:40 +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.
>
> There is likely no bug in the current implementation due to the safeguard:
> > cname[sizeof(cname) - 1] = '\0';
> ... however we can provide simpler and easier to understand code using
> the newer (and recommended) `strscpy` api.
>
> 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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
> ---
> drivers/gpu/drm/nouveau/nvkm/core/firmware.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
> index 91fb494d4009..374212da9e95 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/core/firmware.c
> @@ -79,8 +79,7 @@ nvkm_firmware_get(const struct nvkm_subdev *subdev, const char *fwname, int ver,
> int i;
>
> /* Convert device name to lowercase */
> - strncpy(cname, device->chip->name, sizeof(cname));
> - cname[sizeof(cname) - 1] = '\0';
> + strscpy(cname, device->chip->name, sizeof(cname));
> i = strlen(cname);
> while (i) {
> --i;
>
> ---
> base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
> change-id: 20230914-strncpy-drivers-gpu-drm-nouveau-nvkm-core-firmware-c-791223838b72
>
> Best regards,
> --
> Justin Stitt <[email protected]>
>
--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat