From 710d21fdff9a98d621cd4e64167f3ef8af4e2fd1 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 2 Sep 2022 21:37:49 -0700 Subject: netlink: Bounds-check struct nlmsgerr creation In preparation for FORTIFY_SOURCE doing bounds-check on memcpy(), switch from __nlmsg_put to nlmsg_put(), and explain the bounds check for dealing with the memcpy() across a composite flexible array struct. Avoids this future run-time warning: memcpy: detected field-spanning write (size 32) of single field "&errmsg->msg" at net/netlink/af_netlink.c:2447 (size 16) Cc: Jakub Kicinski Cc: Pablo Neira Ayuso Cc: Jozsef Kadlecsik Cc: Florian Westphal Cc: "David S. Miller" Cc: Eric Dumazet Cc: Paolo Abeni Cc: syzbot Cc: netfilter-devel@vger.kernel.org Cc: coreteam@netfilter.org Cc: netdev@vger.kernel.org Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220901071336.1418572-1-keescook@chromium.org Signed-off-by: David S. Miller --- net/netfilter/ipset/ip_set_core.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'net/netfilter/ipset/ip_set_core.c') diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c index 16ae92054baa..6b31746f9be3 100644 --- a/net/netfilter/ipset/ip_set_core.c +++ b/net/netfilter/ipset/ip_set_core.c @@ -1719,11 +1719,13 @@ call_ad(struct net *net, struct sock *ctnl, struct sk_buff *skb, skb2 = nlmsg_new(payload, GFP_KERNEL); if (!skb2) return -ENOMEM; - rep = __nlmsg_put(skb2, NETLINK_CB(skb).portid, - nlh->nlmsg_seq, NLMSG_ERROR, payload, 0); + rep = nlmsg_put(skb2, NETLINK_CB(skb).portid, + nlh->nlmsg_seq, NLMSG_ERROR, payload, 0); errmsg = nlmsg_data(rep); errmsg->error = ret; - memcpy(&errmsg->msg, nlh, nlh->nlmsg_len); + unsafe_memcpy(&errmsg->msg, nlh, nlh->nlmsg_len, + /* Bounds checked by the skb layer. */); + cmdattr = (void *)&errmsg->msg + min_len; ret = nla_parse(cda, IPSET_ATTR_CMD_MAX, cmdattr, -- cgit v1.2.3-59-g8ed1b