This is a note to let you know that I've just added the patch titled netfilter: socket: icmp6: fix use-after-scope to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: netfilter-socket-icmp6-fix-use-after-scope.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit a048146c561dfee2f068cc078bf109f028f40343 Author: Benjamin Hesmans <benjamin.hesmans@xxxxxxxxxxxx> Date: Fri Sep 3 15:23:35 2021 +0200 netfilter: socket: icmp6: fix use-after-scope [ Upstream commit 730affed24bffcd1eebd5903171960f5ff9f1f22 ] Bug reported by KASAN: BUG: KASAN: use-after-scope in inet6_ehashfn (net/ipv6/inet6_hashtables.c:40) Call Trace: (...) inet6_ehashfn (net/ipv6/inet6_hashtables.c:40) (...) nf_sk_lookup_slow_v6 (net/ipv6/netfilter/nf_socket_ipv6.c:91 net/ipv6/netfilter/nf_socket_ipv6.c:146) It seems that this bug has already been fixed by Eric Dumazet in the past in: commit 78296c97ca1f ("netfilter: xt_socket: fix a stack corruption bug") But a variant of the same issue has been introduced in commit d64d80a2cde9 ("netfilter: x_tables: don't extract flow keys on early demuxed sks in socket match") `daddr` and `saddr` potentially hold a reference to ipv6_var that is no longer in scope when the call to `nf_socket_get_sock_v6` is made. Fixes: d64d80a2cde9 ("netfilter: x_tables: don't extract flow keys on early demuxed sks in socket match") Acked-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx> Signed-off-by: Benjamin Hesmans <benjamin.hesmans@xxxxxxxxxxxx> Reviewed-by: Florian Westphal <fw@xxxxxxxxx> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/ipv6/netfilter/nf_socket_ipv6.c b/net/ipv6/netfilter/nf_socket_ipv6.c index b9df879c48d3..69c021704abd 100644 --- a/net/ipv6/netfilter/nf_socket_ipv6.c +++ b/net/ipv6/netfilter/nf_socket_ipv6.c @@ -99,7 +99,7 @@ struct sock *nf_sk_lookup_slow_v6(struct net *net, const struct sk_buff *skb, { __be16 uninitialized_var(dport), uninitialized_var(sport); const struct in6_addr *daddr = NULL, *saddr = NULL; - struct ipv6hdr *iph = ipv6_hdr(skb); + struct ipv6hdr *iph = ipv6_hdr(skb), ipv6_var; struct sk_buff *data_skb = NULL; int doff = 0; int thoff = 0, tproto; @@ -129,8 +129,6 @@ struct sock *nf_sk_lookup_slow_v6(struct net *net, const struct sk_buff *skb, thoff + sizeof(*hp); } else if (tproto == IPPROTO_ICMPV6) { - struct ipv6hdr ipv6_var; - if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr, &sport, &dport, &ipv6_var)) return NULL;