linux-hardening - [PATCH 54/64] ipv6: Use struct_group() to zero rt6

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Message-Id: <20210727205855.411487-55-keescook@chromium.org>
Date:   Tue, 27 Jul 2021 13:58:45 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-hardening@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Keith Packard <keithpac@...zon.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-staging@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: [PATCH 54/64] ipv6: Use struct_group() to zero rt6_info

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add struct_group() to mark region of struct rt6_info that should be
initialized to zero.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/net/ip6_fib.h | 30 ++++++++++++++++--------------
 net/ipv6/route.c      |  4 +---
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 15b7fbe6b15c..9816e7444918 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -205,20 +205,22 @@ struct fib6_info {
 
 struct rt6_info {
 	struct dst_entry		dst;
-	struct fib6_info __rcu		*from;
-	int				sernum;
-
-	struct rt6key			rt6i_dst;
-	struct rt6key			rt6i_src;
-	struct in6_addr			rt6i_gateway;
-	struct inet6_dev		*rt6i_idev;
-	u32				rt6i_flags;
-
-	struct list_head		rt6i_uncached;
-	struct uncached_list		*rt6i_uncached_list;
-
-	/* more non-fragment space at head required */
-	unsigned short			rt6i_nfheader_len;
+	struct_group(init,
+		struct fib6_info __rcu		*from;
+		int				sernum;
+
+		struct rt6key			rt6i_dst;
+		struct rt6key			rt6i_src;
+		struct in6_addr			rt6i_gateway;
+		struct inet6_dev		*rt6i_idev;
+		u32				rt6i_flags;
+
+		struct list_head		rt6i_uncached;
+		struct uncached_list		*rt6i_uncached_list;
+
+		/* more non-fragment space at head required */
+		unsigned short			rt6i_nfheader_len;
+	);
 };
 
 struct fib6_result {
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 6b8051106aba..bbcc605bab57 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -327,9 +327,7 @@ static const struct rt6_info ip6_blk_hole_entry_template = {
 
 static void rt6_info_init(struct rt6_info *rt)
 {
-	struct dst_entry *dst = &rt->dst;
-
-	memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
+	memset(&rt->init, 0, sizeof(rt->init));
 	INIT_LIST_HEAD(&rt->rt6i_uncached);
 }
 
-- 
2.30.2