[PATCH v2] drm/i915: 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 without
unnecessarily NUL-padding. `ctx` is zero allocated and as such strncpy's
NUL-padding behavior was strictly a performance hit which is now
resolved.

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 at vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt at google.com>
---
Changes in v2:
- drop the `... - 1` (thanks Kees)
- Link to v1: https://lore.kernel.org/r/20230914-strncpy-drivers-gpu-drm-i915-gem-selftests-mock_context-c-v1-1-c3f92df942e0@google.com
---
 drivers/gpu/drm/i915/gem/selftests/mock_context.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/selftests/mock_context.c b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
index 8ac6726ec16b..e199d7dbb876 100644
--- a/drivers/gpu/drm/i915/gem/selftests/mock_context.c
+++ b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
@@ -36,7 +36,7 @@ mock_context(struct drm_i915_private *i915,
 	if (name) {
 		struct i915_ppgtt *ppgtt;
 
-		strncpy(ctx->name, name, sizeof(ctx->name) - 1);
+		strscpy(ctx->name, name, sizeof(ctx->name));
 
 		ppgtt = mock_ppgtt(i915, name);
 		if (!ppgtt)

---
base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
change-id: 20230914-strncpy-drivers-gpu-drm-i915-gem-selftests-mock_context-c-980c8ecc9142

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