[PATCH] platform/surface: aggregator: Annotate struct ssam_event with __counted_by

[Kees Cook]

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct ssam_event.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Maximilian Luz <luzmaximilian@xxxxxxxxx>
Cc: platform-driver-x86@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 include/linux/surface_aggregator/controller.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/surface_aggregator/controller.h b/include/linux/surface_aggregator/controller.h
index cb7980805920..5b67f0f47d80 100644
--- a/include/linux/surface_aggregator/controller.h
+++ b/include/linux/surface_aggregator/controller.h
@@ -44,7 +44,7 @@ struct ssam_event {
 	u8 command_id;
 	u8 instance_id;
 	u16 length;
-	u8 data[];
+	u8 data[] __counted_by(length);
 };
 
 /**
-- 
2.34.1