netdev - [PATCH nf-next 2/7] netfilter: conntrack: Use memset_startat() to zero struct nf

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Message-Id: <20211215234911.170741-3-pablo@netfilter.org>
Date:   Thu, 16 Dec 2021 00:49:06 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, kuba@...nel.org
Subject: [PATCH nf-next 2/7] netfilter: conntrack: Use memset_startat() to zero struct nf_conn

From: Kees Cook <keescook@...omium.org>

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

Use memset_startat() to avoid confusing memset() about writing beyond
the target struct member.

Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_conntrack_core.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 054ee9d25efe..aa657db18318 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1562,9 +1562,7 @@ __nf_conntrack_alloc(struct net *net,
 	ct->status = 0;
 	ct->timeout = 0;
 	write_pnet(&ct->ct_net, net);
-	memset(&ct->__nfct_init_offset, 0,
-	       offsetof(struct nf_conn, proto) -
-	       offsetof(struct nf_conn, __nfct_init_offset));
+	memset_after(ct, 0, __nfct_init_offset);
 
 	nf_ct_zone_add(ct, zone);
 
-- 
2.30.2