Re: [PATCH 1/1] net: gro: fix misuse of CB in udp socket lookup

From: Eric Dumazet
Date: Fri Jul 07 2023 - 09:45:20 EST

On Fri, Jul 7, 2023 at 2:26 PM Richard Gobert <richardbgobert@xxxxxxxxx> wrote:
>
> This patch fixes a misuse of IP{6}CB(skb) in GRO, while calling to
> `udp6_lib_lookup2` when handling udp tunnels. `udp6_lib_lookup2` fetch the
> device from CB. The fix changes it to fetch the device from `skb->dev`.
> l3mdev case requires special attention since it has a master and a slave
> device.
>
> Fixes: a6024562ffd7 ("udp: Add GRO functions to UDP socket")
> Reported-by: Gal Pressman <gal@xxxxxxxxxx>
> Signed-off-by: Richard Gobert <richardbgobert@xxxxxxxxx>
> ---
> include/net/udp.h | 2 ++
> net/ipv4/udp.c | 21 +++++++++++++++++++--
> net/ipv4/udp_offload.c | 7 +++++--
> net/ipv6/udp.c | 21 +++++++++++++++++++--
> net/ipv6/udp_offload.c | 7 +++++--
> 5 files changed, 50 insertions(+), 8 deletions(-)
>
> diff --git a/include/net/udp.h b/include/net/udp.h
> index 4d13424f8f72..48af1479882f 100644
> --- a/include/net/udp.h
> +++ b/include/net/udp.h
> @@ -299,6 +299,7 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
> int udp_lib_setsockopt(struct sock *sk, int level, int optname,
> sockptr_t optval, unsigned int optlen,
> int (*push_pending_frames)(struct sock *));
> +void udp4_get_iif_sdif(const struct sk_buff *skb, int *iif, int *sdif);
> struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
> __be32 daddr, __be16 dport, int dif);
> struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
> @@ -310,6 +311,7 @@ struct sock *udp6_lib_lookup(struct net *net,
> const struct in6_addr *saddr, __be16 sport,
> const struct in6_addr *daddr, __be16 dport,
> int dif);
> +void udp6_get_iif_sdif(const struct sk_buff *skb, int *iif, int *sdif);
> struct sock *__udp6_lib_lookup(struct net *net,
> const struct in6_addr *saddr, __be16 sport,
> const struct in6_addr *daddr, __be16 dport,
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 42a96b3547c9..0581ab184afd 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -550,15 +550,32 @@ static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb,
> inet_sdif(skb), udptable, skb);
> }
>
> +void udp4_get_iif_sdif(const struct sk_buff *skb, int *iif, int *sdif)
> +{
> + *iif = inet_iif(skb) || skb->dev->ifindex;

This looks wrong. Did you mean

*iif = inet_iif(skb) ?: skb->dev->ifindex;

> + *sdif = 0;
> +
> +#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
> + if (netif_is_l3_slave(skb->dev)) {
> + struct net_device *master = netdev_master_upper_dev_get_rcu(skb->dev);
> + *sdif = *iif;
> + *iif = master ? master->ifindex : 0;
> + }
> +#endif
> +}
> +
> struct sock *udp4_lib_lookup_skb(const struct sk_buff *skb,
> __be16 sport, __be16 dport)
> {
> const struct iphdr *iph = ip_hdr(skb);
> struct net *net = dev_net(skb->dev);
> + int iif, sdif;
> +
> + udp4_get_iif_sdif(skb, &iif, &sdif);
>
> return __udp4_lib_lookup(net, iph->saddr, sport,
> - iph->daddr, dport, inet_iif(skb),
> - inet_sdif(skb), net->ipv4.udp_table, NULL);
> + iph->daddr, dport, iif,
> + sdif, net->ipv4.udp_table, NULL);
> }
>
> /* Must be called under rcu_read_lock().
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 75aa4de5b731..70d760b271db 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -603,10 +603,13 @@ static struct sock *udp4_gro_lookup_skb(struct sk_buff *skb, __be16 sport,
> {
> const struct iphdr *iph = skb_gro_network_header(skb);
> struct net *net = dev_net(skb->dev);
> + int iif, sdif;
> +
> + udp4_get_iif_sdif(skb, &iif, &sdif);
>
> return __udp4_lib_lookup(net, iph->saddr, sport,
> - iph->daddr, dport, inet_iif(skb),
> - inet_sdif(skb), net->ipv4.udp_table, NULL);
> + iph->daddr, dport, iif,
> + sdif, net->ipv4.udp_table, NULL);
> }
>
> INDIRECT_CALLABLE_SCOPE
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index 317b01c9bc39..aac9b20d67e4 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -294,15 +294,32 @@ static struct sock *__udp6_lib_lookup_skb(struct sk_buff *skb,
> inet6_sdif(skb), udptable, skb);
> }
>
> +void udp6_get_iif_sdif(const struct sk_buff *skb, int *iif, int *sdif)
> +{
> + *iif = skb->dev->ifindex;

ipv6_rcv() inits

IP6CB(skb)->iif = skb_dst(skb) ?
ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;

You chose to always use skb->dev->ifindex instead ?

You might add a comment why it is okay.

> + *sdif = 0;
> +
> +#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
> + if (netif_is_l3_slave(skb->dev)) {
> + struct net_device *master = netdev_master_upper_dev_get_rcu(skb->dev);
> + *sdif = *iif;
> + *iif = master ? master->ifindex : 0;
> + }
> +#endif
> +}
> +
> struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb,
> __be16 sport, __be16 dport)
> {
> const struct ipv6hdr *iph = ipv6_hdr(skb);
> struct net *net = dev_net(skb->dev);
> + int iif, sdif;
> +
> + udp6_get_iif_sdif(skb, &iif, &sdif);
>
> return __udp6_lib_lookup(net, &iph->saddr, sport,
> - &iph->daddr, dport, inet6_iif(skb),
> - inet6_sdif(skb), net->ipv4.udp_table, NULL);
> + &iph->daddr, dport, iif,
> + sdif, net->ipv4.udp_table, NULL);
> }
>
> /* Must be called under rcu_read_lock().
> diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
> index ad3b8726873e..88191d79002e 100644
> --- a/net/ipv6/udp_offload.c
> +++ b/net/ipv6/udp_offload.c
> @@ -119,10 +119,13 @@ static struct sock *udp6_gro_lookup_skb(struct sk_buff *skb, __be16 sport,
> {
> const struct ipv6hdr *iph = skb_gro_network_header(skb);
> struct net *net = dev_net(skb->dev);
> + int iif, sdif;
> +
> + udp6_get_iif_sdif(skb, &iif, &sdif);
>
> return __udp6_lib_lookup(net, &iph->saddr, sport,
> - &iph->daddr, dport, inet6_iif(skb),
> - inet6_sdif(skb), net->ipv4.udp_table, NULL);
> + &iph->daddr, dport, iif,
> + sdif, net->ipv4.udp_table, NULL);
> }
>
> INDIRECT_CALLABLE_SCOPE
> --
> 2.36.1
>