linux-kernel - [PATCH] gcov: Annotate struct gcov_iterator with __counted

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Message-Id: <20230922175220.work.327-kees@kernel.org>
Date:   Fri, 22 Sep 2023 10:52:20 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Peter Oberparleiter <oberpar@...ux.ibm.com>
Cc:     Kees Cook <keescook@...omium.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] gcov: Annotate struct gcov_iterator 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 gcov_iterator.

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

Cc: Peter Oberparleiter <oberpar@...ux.ibm.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 kernel/gcov/fs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/gcov/fs.c b/kernel/gcov/fs.c
index 5c3086cad8f9..01520689b57c 100644
--- a/kernel/gcov/fs.c
+++ b/kernel/gcov/fs.c
@@ -99,7 +99,7 @@ struct gcov_iterator {
 	struct gcov_info *info;
 	size_t size;
 	loff_t pos;
-	char buffer[];
+	char buffer[] __counted_by(size);
 };
 
 /**
-- 
2.34.1