linux-kernel - [PATCH v2 3/3] linux/fs.h: move member alignment check next to definition of struct filename

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Date:   Fri,  8 Feb 2019 21:30:15 +0100
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        linux-kernel@...r.kernel.org,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: [PATCH v2 3/3] linux/fs.h: move member alignment check next to definition of struct filename

Instead of doing this compile-time check in some slightly arbitrary
user of struct filename, put it next to the definition.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
v2: added, mostly as an example of use of static_assert(), to check
that the compiler actually groks it. Feel free to NAK it as useless
churn.

 fs/namei.c         | 2 --
 include/linux/fs.h | 3 +++
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 914178cdbe94..d604f6b3bcc3 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -39,7 +39,6 @@
 #include <linux/bitops.h>
 #include <linux/init_task.h>
 #include <linux/uaccess.h>
-#include <linux/build_bug.h>
 
 #include "internal.h"
 #include "mount.h"
@@ -131,7 +130,6 @@ getname_flags(const char __user *filename, int flags, int *empty)
 	struct filename *result;
 	char *kname;
 	int len;
-	BUILD_BUG_ON(offsetof(struct filename, iname) % sizeof(long) != 0);
 
 	result = audit_reusename(filename);
 	if (result)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 29d8e2cfed0e..8dce6932e620 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -37,6 +37,8 @@
 #include <linux/uuid.h>
 #include <linux/errseq.h>
 #include <linux/ioprio.h>
+#include <linux/build_bug.h>
+#include <linux/stddef.h>
 
 #include <asm/byteorder.h>
 #include <uapi/linux/fs.h>
@@ -2487,6 +2489,7 @@ struct filename {
 	struct audit_names	*aname;
 	const char		iname[];
 };
+static_assert(offsetof(struct filename, iname) % sizeof(long) == 0);
 
 extern long vfs_truncate(const struct path *, loff_t);
 extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
-- 
2.20.1