`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.
We should NUL-pad as there are full struct copies happening in places:
| struct drm_mode_modeinfo umode;
|
| ...
| struct drm_property_blob *blob;
|
| drm_mode_convert_to_umode(&umode, mode);
| blob = drm_property_create_blob(crtc->dev,
| sizeof(umode), &umode);
A suitable replacement is `strscpy_pad` due to the fact that it
guarantees both NUL-termination and NUL-padding on the destination
buffer.
Additionally, replace size macro `DRM_DISPLAY_MODE_LEN` with sizeof() to
more directly tie the maximum buffer size to the destination buffer:
| struct drm_display_mode {
| ...
| char name[DRM_DISPLAY_MODE_LEN];
Link: https://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@xxxxxxxxxxxxxxx
Cc: Xu Panda <xu.panda@xxxxxxxxxx>
Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
---
Changes in v2:
- use strscpy_pad (thanks Kees)
- rebase onto mainline
- Link to v1: https://lore.kernel.org/r/20230914-strncpy-drivers-gpu-drm-drm_modes-c-v1-1-079b532553a3@xxxxxxxxxx
---
Note: build-tested only.
---
drivers/gpu/drm/drm_modes.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index ac9a406250c5..893f52ee4926 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -2617,8 +2617,7 @@ void drm_mode_convert_to_umode(struct drm_mode_modeinfo *out,
break;
}
- strncpy(out->name, in->name, DRM_DISPLAY_MODE_LEN);
- out->name[DRM_DISPLAY_MODE_LEN-1] = 0;
+ strscpy_pad(out->name, in->name, sizeof(out->name));
}
/**
@@ -2659,8 +2658,7 @@ int drm_mode_convert_umode(struct drm_device *dev,
* useful for the kernel->userspace direction anyway.
*/
out->type = in->type & DRM_MODE_TYPE_ALL;
- strncpy(out->name, in->name, DRM_DISPLAY_MODE_LEN);
- out->name[DRM_DISPLAY_MODE_LEN-1] = 0;
+ strscpy_pad(out->name, in->name, sizeof(out->name));
/* Clearing picture aspect ratio bits from out flags,
* as the aspect-ratio information is not stored in
---
base-commit: 58720809f52779dc0f08e53e54b014209d13eebb
change-id: 20230914-strncpy-drivers-gpu-drm-drm_modes-c-a35d782cad01
Best regards,
--
Justin Stitt <justinstitt@xxxxxxxxxx>
