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    SubjectRe: [PATCH 4.4 002/193] net: replace dst_cache ip6_tunnel implementation with the generic one
    On Fri, Feb 23, 2018 at 07:23:55PM +0100, Greg Kroah-Hartman wrote:
    > 4.4-stable review patch. If anyone has any objections, please let me know.
    >
    > ------------------
    >
    > From: Paolo Abeni <pabeni@redhat.com>
    >
    > commit 607f725f6f7d5ec3759fbc16224afb60e2152a5b upstream.
    >
    > This also fix a potential race into the existing tunnel code, which
    > could lead to the wrong dst to be permanenty cached:
    >
    > CPU1: CPU2:
    > <xmit on ip6_tunnel>
    > <cache lookup fails>
    > dst = ip6_route_output(...)
    > <tunnel params are changed via nl>
    > dst_cache_reset() // no effect,
    > // the cache is empty
    > dst_cache_set() // the wrong dst
    > // is permanenty stored
    > // into the cache
    >
    > With the new dst implementation the above race is not possible
    > since the first cache lookup after dst_cache_reset will fail due
    > to the timestamp check
    >
    > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
    > Suggested-and-acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
    > Signed-off-by: David S. Miller <davem@davemloft.net>
    > Signed-off-by: Manoj Boopathi Raj <manojboopathi@google.com>
    > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    >
    > ---
    > include/net/ip6_tunnel.h | 15 ----
    > net/ipv6/Kconfig | 1
    > net/ipv6/ip6_gre.c | 12 +--
    > net/ipv6/ip6_tunnel.c | 151 +++++++----------------------------------------
    > net/ipv6/ip6_vti.c | 2
    > 5 files changed, 35 insertions(+), 146 deletions(-)
    >
    > --- a/include/net/ip6_tunnel.h
    > +++ b/include/net/ip6_tunnel.h
    > @@ -5,6 +5,8 @@
    > #include <linux/netdevice.h>
    > #include <linux/if_tunnel.h>
    > #include <linux/ip6_tunnel.h>
    > +#include <net/ip_tunnels.h>
    > +#include <net/dst_cache.h>
    >
    > #define IP6TUNNEL_ERR_TIMEO (30*HZ)
    >
    > @@ -32,12 +34,6 @@ struct __ip6_tnl_parm {
    > __be32 o_key;
    > };
    >
    > -struct ip6_tnl_dst {
    > - seqlock_t lock;
    > - struct dst_entry __rcu *dst;
    > - u32 cookie;
    > -};
    > -
    > /* IPv6 tunnel */
    > struct ip6_tnl {
    > struct ip6_tnl __rcu *next; /* next tunnel in list */
    > @@ -45,7 +41,7 @@ struct ip6_tnl {
    > struct net *net; /* netns for packet i/o */
    > struct __ip6_tnl_parm parms; /* tunnel configuration parameters */
    > struct flowi fl; /* flowi template for xmit */
    > - struct ip6_tnl_dst __percpu *dst_cache; /* cached dst */
    > + struct dst_cache dst_cache; /* cached dst */
    >
    > int err_count;
    > unsigned long err_time;
    > @@ -65,11 +61,6 @@ struct ipv6_tlv_tnl_enc_lim {
    > __u8 encap_limit; /* tunnel encapsulation limit */
    > } __packed;
    >
    > -struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t);
    > -int ip6_tnl_dst_init(struct ip6_tnl *t);
    > -void ip6_tnl_dst_destroy(struct ip6_tnl *t);
    > -void ip6_tnl_dst_reset(struct ip6_tnl *t);
    > -void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst);
    > int ip6_tnl_rcv_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,
    > const struct in6_addr *raddr);
    > int ip6_tnl_xmit_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,
    > --- a/net/ipv6/Kconfig
    > +++ b/net/ipv6/Kconfig
    > @@ -205,6 +205,7 @@ config IPV6_NDISC_NODETYPE
    > config IPV6_TUNNEL
    > tristate "IPv6: IP-in-IPv6 tunnel (RFC2473)"
    > select INET6_TUNNEL
    > + select DST_CACHE
    > ---help---
    > Support for IPv6-in-IPv6 and IPv4-in-IPv6 tunnels described in
    > RFC 2473.
    > --- a/net/ipv6/ip6_gre.c
    > +++ b/net/ipv6/ip6_gre.c
    > @@ -362,7 +362,7 @@ static void ip6gre_tunnel_uninit(struct
    > struct ip6gre_net *ign = net_generic(t->net, ip6gre_net_id);
    >
    > ip6gre_tunnel_unlink(ign, t);
    > - ip6_tnl_dst_reset(t);
    > + dst_cache_reset(&t->dst_cache);
    > dev_put(dev);
    > }
    >
    > @@ -640,7 +640,7 @@ static netdev_tx_t ip6gre_xmit2(struct s
    > }
    >
    > if (!fl6->flowi6_mark)
    > - dst = ip6_tnl_dst_get(tunnel);
    > + dst = dst_cache_get(&tunnel->dst_cache);
    >
    > if (!dst) {
    > dst = ip6_route_output(net, NULL, fl6);
    > @@ -709,7 +709,7 @@ static netdev_tx_t ip6gre_xmit2(struct s
    > }
    >
    > if (!fl6->flowi6_mark && ndst)
    > - ip6_tnl_dst_set(tunnel, ndst);
    > + dst_cache_set_ip6(&tunnel->dst_cache, ndst, &fl6->saddr);
    > skb_dst_set(skb, dst);
    >
    > proto = NEXTHDR_GRE;
    > @@ -1017,7 +1017,7 @@ static int ip6gre_tnl_change(struct ip6_
    > t->parms.o_key = p->o_key;
    > t->parms.i_flags = p->i_flags;
    > t->parms.o_flags = p->o_flags;
    > - ip6_tnl_dst_reset(t);
    > + dst_cache_reset(&t->dst_cache);
    > ip6gre_tnl_link_config(t, set_mtu);
    > return 0;
    > }
    > @@ -1228,7 +1228,7 @@ static void ip6gre_dev_free(struct net_d
    > {
    > struct ip6_tnl *t = netdev_priv(dev);
    >
    > - ip6_tnl_dst_destroy(t);
    > + dst_cache_destroy(&t->dst_cache);
    > free_percpu(dev->tstats);
    > free_netdev(dev);
    > }
    > @@ -1266,7 +1266,7 @@ static int ip6gre_tunnel_init_common(str
    > if (!dev->tstats)
    > return -ENOMEM;
    >
    > - ret = ip6_tnl_dst_init(tunnel);
    > + ret = dst_cache_init(&tunnel->dst_cache, GFP_KERNEL);
    > if (ret) {
    > free_percpu(dev->tstats);
    > dev->tstats = NULL;
    > --- a/net/ipv6/ip6_tunnel.c
    > +++ b/net/ipv6/ip6_tunnel.c
    > @@ -122,97 +122,6 @@ static struct net_device_stats *ip6_get_
    > return &dev->stats;
    > }
    >
    > -/*
    > - * Locking : hash tables are protected by RCU and RTNL
    > - */
    > -
    > -static void ip6_tnl_per_cpu_dst_set(struct ip6_tnl_dst *idst,
    > - struct dst_entry *dst)
    > -{
    > - write_seqlock_bh(&idst->lock);
    > - dst_release(rcu_dereference_protected(
    > - idst->dst,
    > - lockdep_is_held(&idst->lock.lock)));
    > - if (dst) {
    > - dst_hold(dst);
    > - idst->cookie = rt6_get_cookie((struct rt6_info *)dst);
    > - } else {
    > - idst->cookie = 0;
    > - }
    > - rcu_assign_pointer(idst->dst, dst);
    > - write_sequnlock_bh(&idst->lock);
    > -}
    > -
    > -struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t)
    > -{
    > - struct ip6_tnl_dst *idst;
    > - struct dst_entry *dst;
    > - unsigned int seq;
    > - u32 cookie;
    > -
    > - idst = raw_cpu_ptr(t->dst_cache);
    > -
    > - rcu_read_lock();
    > - do {
    > - seq = read_seqbegin(&idst->lock);
    > - dst = rcu_dereference(idst->dst);
    > - cookie = idst->cookie;
    > - } while (read_seqretry(&idst->lock, seq));
    > -
    > - if (dst && !atomic_inc_not_zero(&dst->__refcnt))
    > - dst = NULL;
    > - rcu_read_unlock();
    > -
    > - if (dst && dst->obsolete && !dst->ops->check(dst, cookie)) {
    > - ip6_tnl_per_cpu_dst_set(idst, NULL);
    > - dst_release(dst);
    > - dst = NULL;
    > - }
    > - return dst;
    > -}
    > -EXPORT_SYMBOL_GPL(ip6_tnl_dst_get);
    > -
    > -void ip6_tnl_dst_reset(struct ip6_tnl *t)
    > -{
    > - int i;
    > -
    > - for_each_possible_cpu(i)
    > - ip6_tnl_per_cpu_dst_set(per_cpu_ptr(t->dst_cache, i), NULL);
    > -}
    > -EXPORT_SYMBOL_GPL(ip6_tnl_dst_reset);
    > -
    > -void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst)
    > -{
    > - ip6_tnl_per_cpu_dst_set(raw_cpu_ptr(t->dst_cache), dst);
    > -
    > -}
    > -EXPORT_SYMBOL_GPL(ip6_tnl_dst_set);
    > -
    > -void ip6_tnl_dst_destroy(struct ip6_tnl *t)
    > -{
    > - if (!t->dst_cache)
    > - return;
    > -
    > - ip6_tnl_dst_reset(t);
    > - free_percpu(t->dst_cache);
    > -}
    > -EXPORT_SYMBOL_GPL(ip6_tnl_dst_destroy);
    > -
    > -int ip6_tnl_dst_init(struct ip6_tnl *t)
    > -{
    > - int i;
    > -
    > - t->dst_cache = alloc_percpu(struct ip6_tnl_dst);
    > - if (!t->dst_cache)
    > - return -ENOMEM;
    > -
    > - for_each_possible_cpu(i)
    > - seqlock_init(&per_cpu_ptr(t->dst_cache, i)->lock);
    > -
    > - return 0;
    > -}
    > -EXPORT_SYMBOL_GPL(ip6_tnl_dst_init);
    > -
    > /**
    > * ip6_tnl_lookup - fetch tunnel matching the end-point addresses
    > * @remote: the address of the tunnel exit-point
    > @@ -331,7 +240,7 @@ static void ip6_dev_free(struct net_devi
    > {
    > struct ip6_tnl *t = netdev_priv(dev);
    >
    > - ip6_tnl_dst_destroy(t);
    > + dst_cache_destroy(&t->dst_cache);
    > free_percpu(dev->tstats);
    > free_netdev(dev);
    > }
    > @@ -464,7 +373,7 @@ ip6_tnl_dev_uninit(struct net_device *de
    > RCU_INIT_POINTER(ip6n->tnls_wc[0], NULL);
    > else
    > ip6_tnl_unlink(ip6n, t);
    > - ip6_tnl_dst_reset(t);
    > + dst_cache_reset(&t->dst_cache);
    > dev_put(dev);
    > }
    >
    > @@ -1053,7 +962,6 @@ static int ip6_tnl_xmit2(struct sk_buff
    > struct ipv6_tel_txoption opt;
    > struct dst_entry *dst = NULL, *ndst = NULL;
    > struct net_device *tdev;
    > - bool use_cache = false;
    > int mtu;
    > unsigned int max_headroom = sizeof(struct ipv6hdr);
    > u8 proto;
    > @@ -1061,39 +969,28 @@ static int ip6_tnl_xmit2(struct sk_buff
    >
    > /* NBMA tunnel */
    > if (ipv6_addr_any(&t->parms.raddr)) {
    > - if (skb->protocol == htons(ETH_P_IPV6)) {
    > - struct in6_addr *addr6;
    > - struct neighbour *neigh;
    > - int addr_type;
    > -
    > - if (!skb_dst(skb))
    > - goto tx_err_link_failure;
    > -
    > - neigh = dst_neigh_lookup(skb_dst(skb),
    > - &ipv6_hdr(skb)->daddr);
    > - if (!neigh)
    > - goto tx_err_link_failure;
    > + struct in6_addr *addr6;
    > + struct neighbour *neigh;
    > + int addr_type;
    > +
    > + if (!skb_dst(skb))
    > + goto tx_err_link_failure;
    >
    > - addr6 = (struct in6_addr *)&neigh->primary_key;
    > - addr_type = ipv6_addr_type(addr6);
    > + neigh = dst_neigh_lookup(skb_dst(skb),
    > + &ipv6_hdr(skb)->daddr);
    > + if (!neigh)
    > + goto tx_err_link_failure;
    >
    > - if (addr_type == IPV6_ADDR_ANY)
    > - addr6 = &ipv6_hdr(skb)->daddr;
    > + addr6 = (struct in6_addr *)&neigh->primary_key;
    > + addr_type = ipv6_addr_type(addr6);
    >
    > - memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
    > - neigh_release(neigh);
    > - }
    > - } else if (t->parms.proto != 0 && !(t->parms.flags &
    > - (IP6_TNL_F_USE_ORIG_TCLASS |
    > - IP6_TNL_F_USE_ORIG_FWMARK))) {
    > - /* enable the cache only if neither the outer protocol nor the
    > - * routing decision depends on the current inner header value
    > - */
    > - use_cache = true;
    > - }
    > + if (addr_type == IPV6_ADDR_ANY)
    > + addr6 = &ipv6_hdr(skb)->daddr;
    >
    > - if (use_cache)
    > - dst = ip6_tnl_dst_get(t);
    > + memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
    > + neigh_release(neigh);
    > + } else if (!fl6->flowi6_mark)
    > + dst = dst_cache_get(&t->dst_cache);
    >
    > if (!ip6_tnl_xmit_ctl(t, &fl6->saddr, &fl6->daddr))
    > goto tx_err_link_failure;
    > @@ -1156,8 +1053,8 @@ static int ip6_tnl_xmit2(struct sk_buff
    > skb = new_skb;
    > }
    >
    > - if (use_cache && ndst)
    > - ip6_tnl_dst_set(t, ndst);
    > + if (!fl6->flowi6_mark && ndst)
    > + dst_cache_set_ip6(&t->dst_cache, ndst, &fl6->saddr);
    > skb_dst_set(skb, dst);
    >
    > skb->transport_header = skb->network_header;
    > @@ -1392,7 +1289,7 @@ ip6_tnl_change(struct ip6_tnl *t, const
    > t->parms.flowinfo = p->flowinfo;
    > t->parms.link = p->link;
    > t->parms.proto = p->proto;
    > - ip6_tnl_dst_reset(t);
    > + dst_cache_reset(&t->dst_cache);
    > ip6_tnl_link_config(t);
    > return 0;
    > }
    > @@ -1663,7 +1560,7 @@ ip6_tnl_dev_init_gen(struct net_device *
    > if (!dev->tstats)
    > return -ENOMEM;
    >
    > - ret = ip6_tnl_dst_init(t);
    > + ret = dst_cache_init(&t->dst_cache, GFP_KERNEL);
    > if (ret) {
    > free_percpu(dev->tstats);
    > dev->tstats = NULL;
    > --- a/net/ipv6/ip6_vti.c
    > +++ b/net/ipv6/ip6_vti.c
    > @@ -645,7 +645,7 @@ vti6_tnl_change(struct ip6_tnl *t, const
    > t->parms.i_key = p->i_key;
    > t->parms.o_key = p->o_key;
    > t->parms.proto = p->proto;
    > - ip6_tnl_dst_reset(t);
    > + dst_cache_reset(&t->dst_cache);
    > vti6_link_config(t);
    > return 0;
    > }
    >
    >

    It may also be wise to take these two commits from mainline, as they
    are along the same lines as this one:

    09acddf873b ("ip_tunnel: replace dst_cache with generic implementation")
    27337e16f2d ("ip_tunnel: fix preempt warning in ip tunnel creation/updating")

    There is a minor conflict with the first one due to stable commit
    6f99825e7632 ("sit: fix a double free on error path").

    I'll most likely carry them anyways, it fixes a build error with some
    out of tree code but less out of tree code I have, the better!

    Thanks!
    Nathan

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