linux-hardening - [PATCH] input: Annotate struct evdev_client with __counted

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Date: Fri, 22 Sep 2023 10:50:28 -0700
From: Kees Cook <keescook@...omium.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: Kees Cook <keescook@...omium.org>,
	linux-input@...r.kernel.org,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Tom Rix <trix@...hat.com>,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev,
	linux-hardening@...r.kernel.org
Subject: [PATCH] input: Annotate struct evdev_client with __counted_by

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 evdev_client.

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

Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: linux-input@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/input/evdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 95f90699d2b1..51e0c4954600 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -50,7 +50,7 @@ struct evdev_client {
 	bool revoked;
 	unsigned long *evmasks[EV_CNT];
 	unsigned int bufsize;
-	struct input_event buffer[];
+	struct input_event buffer[] __counted_by(bufsize);
 };
 
 static size_t evdev_get_mask_cnt(unsigned int type)
-- 
2.34.1