linux-hardening - [PATCH v2 1/2] stddef: Allow attributes to be used when creating flex arrays

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Date: Tue, 13 Feb 2024 15:42:10 -0800
From: Kees Cook <keescook@...omium.org>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Dan Williams <dan.j.williams@...el.com>,
	Keith Packard <keithp@...thp.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Dmitry Antipov <dmantipov@...dex.ru>,
	"Gustavo A . R . Silva" <gustavoars@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Nathan Chancellor <nathan@...nel.org>,
	kernel test robot <lkp@...el.com>,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH v2 1/2] stddef: Allow attributes to be used when creating flex arrays

With the coming support for the __counted_by struct member attribute,
we will need a way to add such annotations to the places where
DECLARE_FLEX_ARRAY() is used. Add an optional 3rd argument that can be
used for including attributes in the flexible array definition.

Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Keith Packard <keithp@...thp.com>
Cc: Miguel Ojeda <ojeda@...nel.org>
Cc: Alexey Dobriyan <adobriyan@...il.com>
Cc: Dmitry Antipov <dmantipov@...dex.ru>
Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/stddef.h      |  6 +++---
 include/uapi/linux/stddef.h | 10 +++++-----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/stddef.h b/include/linux/stddef.h
index 929d67710cc5..176bfe8c0bd7 100644
--- a/include/linux/stddef.h
+++ b/include/linux/stddef.h
@@ -82,15 +82,15 @@ enum {
 
 /**
  * DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
- *
  * @TYPE: The type of each flexible array element
  * @NAME: The name of the flexible array member
+ * @...: The list of member attributes to apply (optional)
  *
  * In order to have a flexible array member in a union or alone in a
  * struct, it needs to be wrapped in an anonymous struct with at least 1
  * named member, but that member can be empty.
  */
-#define DECLARE_FLEX_ARRAY(TYPE, NAME) \
-	__DECLARE_FLEX_ARRAY(TYPE, NAME)
+#define DECLARE_FLEX_ARRAY(TYPE, NAME, ...) \
+	__DECLARE_FLEX_ARRAY(TYPE, NAME, __VA_ARGS__)
 
 #endif
diff --git a/include/uapi/linux/stddef.h b/include/uapi/linux/stddef.h
index 2ec6f35cda32..028aeec3d7f1 100644
--- a/include/uapi/linux/stddef.h
+++ b/include/uapi/linux/stddef.h
@@ -31,23 +31,23 @@
 
 #ifdef __cplusplus
 /* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
-#define __DECLARE_FLEX_ARRAY(T, member)	\
-	T member[0]
+#define __DECLARE_FLEX_ARRAY(TYPE, NAME, ...)	\
+	TYPE NAME[0] __VA_ARGS__
 #else
 /**
  * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
- *
  * @TYPE: The type of each flexible array element
  * @NAME: The name of the flexible array member
+ * @...: The list of member attributes to apply (optional)
  *
  * In order to have a flexible array member in a union or alone in a
  * struct, it needs to be wrapped in an anonymous struct with at least 1
  * named member, but that member can be empty.
  */
-#define __DECLARE_FLEX_ARRAY(TYPE, NAME)	\
+#define __DECLARE_FLEX_ARRAY(TYPE, NAME, ...)	\
 	struct { \
 		struct { } __empty_ ## NAME; \
-		TYPE NAME[]; \
+		TYPE NAME[] __VA_ARGS__; \
 	}
 #endif
 
-- 
2.34.1