[PATCH] netfilter: conntrack: Use memset_startat() to zero struct nf_conn

From: Kees Cook
Date: Thu Nov 18 2021 - 15:31:18 EST


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@xxxxxxxxxxxx>
---
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 770a63103c7a..cdfb63509501 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