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netlink: Bounds-check struct nlmsgerr creation

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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 <kuba@kernel.org>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Jozsef Kadlecsik <kadlec@netfilter.org>
Cc: Florian Westphal <fw@strlen.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: syzbot <syzkaller@googlegroups.com>
Cc: netfilter-devel@vger.kernel.org
Cc: coreteam@netfilter.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220901071336.1418572-1-keescook@chromium.org
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kees Cook 2022-09-02 21:37:49 -07:00 committed by David S. Miller
parent 05ad5d4581
commit 710d21fdff
2 changed files with 10 additions and 6 deletions
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8
net/netfilter/ipset/ip_set_core.c
View File

@ -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,

8
net/netlink/af_netlink.c
View File

@ -2494,11 +2494,13 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
return;
}
rep = __nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
NLMSG_ERROR, payload, flags);
rep = nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
NLMSG_ERROR, payload, flags);
errmsg = nlmsg_data(rep);
errmsg->error = err;
memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh));
unsafe_memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg)
? nlh->nlmsg_len : sizeof(*nlh),
/* Bounds checked by the skb layer. */);
if (tlvlen)
netlink_ack_tlv_fill(in_skb, skb, nlh, err, extack);