[kernel-hardening] [PATCH 05/38] stddef.h: Introduce sizeof_field()

Kees Cook
2018-01-11T02:02:37Z

The size of fields within a structure is needed in a few places in the
kernel already, and will be needed for the usercopy whitelisting when
declaring whitelist regions within structures. This creates a dedicated
macro and redefines offsetofend() to use it.

Existing usage, ignoring the 1200+ lustre assert uses:

$ git grep -E 'sizeof\(\(\((struct )?[a-zA-Z_]+ \*\)0\)->' | \
grep -v staging/lustre | wc -l
65

Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/linux/stddef.h | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/linux/stddef.h b/include/linux/stddef.h
index 2181719fd907..998a4ba28eba 100644
--- a/include/linux/stddef.h
+++ b/include/linux/stddef.h
@@ -20,12 +20,20 @@ enum {
#endif

/**
+ * sizeof_field(TYPE, MEMBER)
+ *
+ * @TYPE: The structure containing the field of interest
+ * @MEMBER: The field to return the size of
+ */
+#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
+
+/**
* offsetofend(TYPE, MEMBER)
*
* @TYPE: The type of the structure
* @MEMBER: The member within the structure to get the end offset of
*/
#define offsetofend(TYPE, MEMBER) \
- (offsetof(TYPE, MEMBER) + sizeof(((TYPE *)0)->MEMBER))
+ (offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))

#endif
--
2.7.4