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 <luzmaximil...@gmail.com>
Cc: platform-driver-...@vger.kernel.org
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 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


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