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Message-ID: <Z-KdsLBF9lCM1m34@krikkit>
Date: Tue, 25 Mar 2025 13:12:32 +0100
From: Sabrina Dubroca <sd@...asysnail.net>
To: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Simon Horman <horms@...nel.org>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>,
David Ahern <dsahern@...nel.org>,
Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH net-next v2 1/5] udp_tunnel: properly deal with xfrm gro
encap.
2025-03-21, 12:52:52 +0100, Paolo Abeni wrote:
> The blamed commit below does not take in account that xfrm
> can enable GRO over UDP encapsulation without going through
> setup_udp_tunnel_sock().
>
> At deletion time such socket will still go through
> udp_tunnel_cleanup_gro(), and the failed GRO type lookup will
> trigger the reported warning.
>
> Add the GRO accounting for XFRM tunnel when GRO is enabled, and
> adjust the known gro types accordingly.
>
> Note that we can't use setup_udp_tunnel_sock() here, as the xfrm
> tunnel setup can be "incremental" - e.g. the encapsulation is created
> first and GRO is enabled later.
>
> Also we can not allow GRO sk lookup optimization for XFRM tunnels, as
> the socket could match the selection criteria at enable time, and
> later on the user-space could disconnect/bind it breaking such
> criteria.
>
> Reported-by: syzbot+8c469a2260132cd095c1@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=8c469a2260132cd095c1
> Fixes: 311b36574ceac ("udp_tunnel: use static call for GRO hooks when possible")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---
> v1 -> v2:
> - do proper account for xfrm, retain the warning
> ---
> net/ipv4/udp.c | 5 +++++
> net/ipv4/udp_offload.c | 4 +++-
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index db606f7e41638..79efbf465fb04 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -2903,10 +2903,15 @@ static void set_xfrm_gro_udp_encap_rcv(__u16 encap_type, unsigned short family,
> {
> #ifdef CONFIG_XFRM
> if (udp_test_bit(GRO_ENABLED, sk) && encap_type == UDP_ENCAP_ESPINUDP) {
> + bool old_enabled = !!udp_sk(sk)->gro_receive;
> +
> if (family == AF_INET)
> WRITE_ONCE(udp_sk(sk)->gro_receive, xfrm4_gro_udp_encap_rcv);
> else if (IS_ENABLED(CONFIG_IPV6) && family == AF_INET6)
> WRITE_ONCE(udp_sk(sk)->gro_receive, ipv6_stub->xfrm6_gro_udp_encap_rcv);
> +
> + if (!old_enabled && udp_sk(sk)->gro_receive)
> + udp_tunnel_update_gro_rcv(sk, true);
We're not under any lock at this point, so this is a bit racy. I think
we'll "only" end up leaking a ref on cur->count if this happens. Not
ideal, but much better than the current situation.
> }
> #endif
> }
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 088aa8cb8ac0c..02365b818f1af 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -37,9 +37,11 @@ struct udp_tunnel_type_entry {
> refcount_t count;
> };
>
> +/* vxlan, fou and xfrm have 2 different gro_receive hooks each */
> #define UDP_MAX_TUNNEL_TYPES (IS_ENABLED(CONFIG_GENEVE) + \
> IS_ENABLED(CONFIG_VXLAN) * 2 + \
> - IS_ENABLED(CONFIG_NET_FOU) * 2)
> + IS_ENABLED(CONFIG_NET_FOU) * 2 + \
> + IS_ENABLED(CONFIG_XFRM) * 2)
>
> DEFINE_STATIC_CALL(udp_tunnel_gro_rcv, dummy_gro_rcv);
> static DEFINE_STATIC_KEY_FALSE(udp_tunnel_static_call);
> --
> 2.48.1
>
>
--
Sabrina
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