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    Subject[PATCH 4.19 289/293] netfilter: socket: icmp6: fix use-after-scope
    Date
    From: Benjamin Hesmans <benjamin.hesmans@tessares.net>

    [ 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@tessares.net>
    Signed-off-by: Benjamin Hesmans <benjamin.hesmans@tessares.net>
    Reviewed-by: Florian Westphal <fw@strlen.de>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/ipv6/netfilter/nf_socket_ipv6.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    diff --git a/net/ipv6/netfilter/nf_socket_ipv6.c b/net/ipv6/netfilter/nf_socket_ipv6.c
    index f14de4b6d639..58e839e2ce1d 100644
    --- a/net/ipv6/netfilter/nf_socket_ipv6.c
    +++ b/net/ipv6/netfilter/nf_socket_ipv6.c
    @@ -104,7 +104,7 @@ 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;
    @@ -134,8 +134,6 @@ 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;
    --
    2.30.2


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