From 8207f253a097fe15c93d85ac15ebb73c5e39e1e1 Mon Sep 17 00:00:00 2001 From: Thomas Zeitlhofer Date: Tue, 15 Nov 2022 23:09:41 +0100 Subject: [PATCH] net: neigh: decrement the family specific qlen Commit 0ff4eb3d5ebb ("neighbour: make proxy_queue.qlen limit per-device") introduced the length counter qlen in struct neigh_parms. There are separate neigh_parms instances for IPv4/ARP and IPv6/ND, and while the family specific qlen is incremented in pneigh_enqueue(), the mentioned commit decrements always the IPv4/ARP specific qlen, regardless of the currently processed family, in pneigh_queue_purge() and neigh_proxy_process(). As a result, with IPv6/ND, the family specific qlen is only incremented (and never decremented) until it exceeds PROXY_QLEN, and then, according to the check in pneigh_enqueue(), neighbor solicitations are not answered anymore. As an example, this is noted when using the subnet-router anycast address to access a Linux router. After a certain amount of time (in the observed case, qlen exceeded PROXY_QLEN after two days), the Linux router stops answering neighbor solicitations for its subnet-router anycast address and effectively becomes unreachable. Another result with IPv6/ND is that the IPv4/ARP specific qlen is decremented more often than incremented. This leads to negative qlen values, as a signed integer has been used for the length counter qlen, and potentially to an integer overflow. Fix this by introducing the helper function neigh_parms_qlen_dec(), which decrements the family specific qlen. Thereby, make use of the existing helper function neigh_get_dev_parms_rcu(), whose definition therefore needs to be placed earlier in neighbour.c. Take the family member from struct neigh_table to determine the currently processed family and appropriately call neigh_parms_qlen_dec() from pneigh_queue_purge() and neigh_proxy_process(). Additionally, use an unsigned integer for the length counter qlen. Fixes: 0ff4eb3d5ebb ("neighbour: make proxy_queue.qlen limit per-device") Signed-off-by: Thomas Zeitlhofer Signed-off-by: David S. Miller --- include/net/neighbour.h | 2 +- net/core/neighbour.c | 58 +++++++++++++++++++++++++------------------------ 2 files changed, 31 insertions(+), 29 deletions(-) diff --git a/include/net/neighbour.h b/include/net/neighbour.h index 20745cf..2f2a602 100644 --- a/include/net/neighbour.h +++ b/include/net/neighbour.h @@ -83,7 +83,7 @@ struct neigh_parms { struct rcu_head rcu_head; int reachable_time; - int qlen; + u32 qlen; int data[NEIGH_VAR_DATA_MAX]; DECLARE_BITMAP(data_state, NEIGH_VAR_DATA_MAX); }; diff --git a/net/core/neighbour.c b/net/core/neighbour.c index a77a85e..952a547 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -307,7 +307,31 @@ static int neigh_del_timer(struct neighbour *n) return 0; } -static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net) +static struct neigh_parms *neigh_get_dev_parms_rcu(struct net_device *dev, + int family) +{ + switch (family) { + case AF_INET: + return __in_dev_arp_parms_get_rcu(dev); + case AF_INET6: + return __in6_dev_nd_parms_get_rcu(dev); + } + return NULL; +} + +static void neigh_parms_qlen_dec(struct net_device *dev, int family) +{ + struct neigh_parms *p; + + rcu_read_lock(); + p = neigh_get_dev_parms_rcu(dev, family); + if (p) + p->qlen--; + rcu_read_unlock(); +} + +static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net, + int family) { struct sk_buff_head tmp; unsigned long flags; @@ -321,13 +345,7 @@ static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net) struct net_device *dev = skb->dev; if (net == NULL || net_eq(dev_net(dev), net)) { - struct in_device *in_dev; - - rcu_read_lock(); - in_dev = __in_dev_get_rcu(dev); - if (in_dev) - in_dev->arp_parms->qlen--; - rcu_read_unlock(); + neigh_parms_qlen_dec(dev, family); __skb_unlink(skb, list); __skb_queue_tail(&tmp, skb); } @@ -409,7 +427,8 @@ static int __neigh_ifdown(struct neigh_table *tbl, struct net_device *dev, write_lock_bh(&tbl->lock); neigh_flush_dev(tbl, dev, skip_perm); pneigh_ifdown_and_unlock(tbl, dev); - pneigh_queue_purge(&tbl->proxy_queue, dev ? dev_net(dev) : NULL); + pneigh_queue_purge(&tbl->proxy_queue, dev ? dev_net(dev) : NULL, + tbl->family); if (skb_queue_empty_lockless(&tbl->proxy_queue)) del_timer_sync(&tbl->proxy_timer); return 0; @@ -1621,13 +1640,8 @@ static void neigh_proxy_process(struct timer_list *t) if (tdif <= 0) { struct net_device *dev = skb->dev; - struct in_device *in_dev; - rcu_read_lock(); - in_dev = __in_dev_get_rcu(dev); - if (in_dev) - in_dev->arp_parms->qlen--; - rcu_read_unlock(); + neigh_parms_qlen_dec(dev, tbl->family); __skb_unlink(skb, &tbl->proxy_queue); if (tbl->proxy_redo && netif_running(dev)) { @@ -1821,7 +1835,7 @@ int neigh_table_clear(int index, struct neigh_table *tbl) cancel_delayed_work_sync(&tbl->managed_work); cancel_delayed_work_sync(&tbl->gc_work); del_timer_sync(&tbl->proxy_timer); - pneigh_queue_purge(&tbl->proxy_queue, NULL); + pneigh_queue_purge(&tbl->proxy_queue, NULL, tbl->family); neigh_ifdown(tbl, NULL); if (atomic_read(&tbl->entries)) pr_crit("neighbour leakage\n"); @@ -3539,18 +3553,6 @@ static int proc_unres_qlen(struct ctl_table *ctl, int write, return ret; } -static struct neigh_parms *neigh_get_dev_parms_rcu(struct net_device *dev, - int family) -{ - switch (family) { - case AF_INET: - return __in_dev_arp_parms_get_rcu(dev); - case AF_INET6: - return __in6_dev_nd_parms_get_rcu(dev); - } - return NULL; -} - static void neigh_copy_dflt_parms(struct net *net, struct neigh_parms *p, int index) { -- 2.7.4