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Date: Wed, 10 Jan 2018 18:02:37 -0800
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Windsor <dave@...lcore.net>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Christoph Lameter <cl@...ux.com>,
	"David S. Miller" <davem@...emloft.net>,
	Laura Abbott <labbott@...hat.com>,
	Mark Rutland <mark.rutland@....com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Dave Kleikamp <dave.kleikamp@...cle.com>,
	Jan Kara <jack@...e.cz>,
	Luis de Bethencourt <luisbg@...nel.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Rik van Riel <riel@...hat.com>,
	Matthew Garrett <mjg59@...gle.com>,
	linux-fsdevel@...r.kernel.org,
	linux-arch@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-mm@...ck.org,
	kernel-hardening@...ts.openwall.com
Subject: [PATCH 05/38] stddef.h: Introduce sizeof_field()

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@...omium.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

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