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[for-next,23/25] xfrm: Use memset_after() to clear padding

Message ID 20210822075122.864511-24-keescook@chromium.org (mailing list archive)
State New
Headers show
Series Prepare for better FORTIFY_SOURCE | expand

Commit Message

Kees Cook Aug. 22, 2021, 7:51 a.m. UTC 
In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Clear trailing padding bytes using the new helper so that memset()
doesn't get confused about writing "past the end" of the last struct
member. There is no change to the resulting machine code.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 net/xfrm/xfrm_policy.c | 4 +---
 net/xfrm/xfrm_user.c   | 2 +-
 2 files changed, 2 insertions(+), 4 deletions(-)
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Patch

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 827d84255021..a21af241a2bb 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2494,9 +2494,7 @@  static inline struct xfrm_dst *xfrm_alloc_dst(struct net *net, int family)
 	xdst = dst_alloc(dst_ops, NULL, 1, DST_OBSOLETE_NONE, 0);
 
 	if (likely(xdst)) {
-		struct dst_entry *dst = &xdst->u.dst;
-
-		memset(dst + 1, 0, sizeof(*xdst) - sizeof(*dst));
+		memset_after(xdst, 0, u.dst);
 	} else
 		xdst = ERR_PTR(-ENOBUFS);
 
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index b47d613409b7..880d260541c9 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -2845,7 +2845,7 @@  static int build_expire(struct sk_buff *skb, struct xfrm_state *x, const struct
 	copy_to_user_state(x, &ue->state);
 	ue->hard = (c->data.hard != 0) ? 1 : 0;
 	/* clear the padding bytes */
-	memset(&ue->hard + 1, 0, sizeof(*ue) - offsetofend(typeof(*ue), hard));
+	memset_after(ue, 0, hard);
 
 	err = xfrm_mark_put(skb, &x->mark);
 	if (err)