On Thu, 2017-07-27 at 00:06 -0700, Eric Dumazet wrote: > On Wed, 2017-07-26 at 17:29 +0200, Paolo Abeni wrote: > > When an early demuxed packet reaches __udp6_lib_lookup_skb(), the > > sk reference is retrieved and used, but the relevant reference > > count is leaked and the socket destructor is never called. > > Beyond leaking the sk memory, if there are pending UDP packets > > in the receive queue, even the related accounted memory is leaked. > > > > In the long run, this will cause persistent forward allocation errors > > and no UDP skbs (both ipv4 and ipv6) will be able to reach the > > user-space. > > > > Fix this by explicitly accessing the early demux reference before > > the lookup, and properly decreasing the socket reference count > > after usage. > > > > Also drop the skb_steal_sock() in __udp6_lib_lookup_skb(), and > > the now obsoleted comment about "socket cache". > > > > The newly added code is derived from the current ipv4 code for the > > similar path. > > > Nice catch Paolo. > > I believe there is one point to discuss, see below. > > > > > Reported-by: Sam Edwards <[email protected]> > > Reported-by: Marc Haber <[email protected]> > > Fixes: 5425077d73e0 ("net: ipv6: Add early demux handler for UDP unicast") > > Signed-off-by: Paolo Abeni <[email protected]> > > --- > > include/net/udp.h | 1 + > > net/ipv4/udp.c | 3 ++- > > net/ipv6/udp.c | 28 +++++++++++++++++++--------- > > 3 files changed, 22 insertions(+), 10 deletions(-) > > > > diff --git a/include/net/udp.h b/include/net/udp.h > > index 56ce2d2a612d..cc8036987dcb 100644 > > --- a/include/net/udp.h > > +++ b/include/net/udp.h > > @@ -260,6 +260,7 @@ static inline struct sk_buff *skb_recv_udp(struct sock > > *sk, unsigned int flags, > > } > > > > void udp_v4_early_demux(struct sk_buff *skb); > > +void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst); > > int udp_get_port(struct sock *sk, unsigned short snum, > > int (*saddr_cmp)(const struct sock *, > > const struct sock *)); > > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c > > index fac7cb9e3b0f..e6276fa3750b 100644 > > --- a/net/ipv4/udp.c > > +++ b/net/ipv4/udp.c > > @@ -1928,7 +1928,7 @@ static int udp_queue_rcv_skb(struct sock *sk, struct > > sk_buff *skb) > > /* For TCP sockets, sk_rx_dst is protected by socket lock > > * For UDP, we use xchg() to guard against concurrent changes. > > */ > > -static void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst) > > +void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst) > > { > > struct dst_entry *old; > > > > @@ -1937,6 +1937,7 @@ static void udp_sk_rx_dst_set(struct sock *sk, struct > > dst_entry *dst) > > dst_release(old); > > } > > } > > +EXPORT_SYMBOL(udp_sk_rx_dst_set); > > > > /* > > * Multicasts and broadcasts go to each listener. > > diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c > > index 4a3e65626e8b..e74fe497d823 100644 > > --- a/net/ipv6/udp.c > > +++ b/net/ipv6/udp.c > > @@ -291,11 +291,7 @@ static struct sock *__udp6_lib_lookup_skb(struct > > sk_buff *skb, > > struct udp_table *udptable) > > { > > const struct ipv6hdr *iph = ipv6_hdr(skb); > > - struct sock *sk; > > > > - sk = skb_steal_sock(skb); > > - if (unlikely(sk)) > > - return sk; > > return __udp6_lib_lookup(dev_net(skb->dev), &iph->saddr, sport, > > &iph->daddr, dport, inet6_iif(skb), > > udptable, skb); > > @@ -804,6 +800,25 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct > > udp_table *udptable, > > if (udp6_csum_init(skb, uh, proto)) > > goto csum_error; > > > > + /* Check if the socket is already available, e.g. due to early demux */ > > + sk = skb_steal_sock(skb); > > + if (sk) { > > + struct dst_entry *dst = skb_dst(skb); > > + int ret; > > + > > + if (unlikely(sk->sk_rx_dst != dst)) > > + udp_sk_rx_dst_set(sk, dst); > > + > > + ret = udpv6_queue_rcv_skb(sk, skb); > > + sock_put(sk); > > + /* a return value > 0 means to resubmit the input, but > > + * it wants the return to be -protocol, or 0 > > + */ > > + if (ret > 0) > > + return -ret; > > IPv6 and IPv4 have different behavior for resubmit > > I believe "return ret;" would be more appropriate here.
Thank you for the feedback! You are very right. I stared at the correct UDPv6 code for unicast packets, a few lines below, for a lot of time before noticing the difference :-( I'll resubmit a v2 soon, thanks! Paolo
