-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: Wolfgang Bumiller <w.bumiller@proxmox.com>
-Date: Mon, 9 Apr 2018 14:56:29 +0200
-Subject: [PATCH] net: fix deadlock while clearing neighbor proxy table
-
-When coming from ndisc_netdev_event() in net/ipv6/ndisc.c,
-neigh_ifdown() is called with &nd_tbl, locking this while
-clearing the proxy neighbor entries when eg. deleting an
-interface. Calling the table's pndisc_destructor() with the
-lock still held, however, can cause a deadlock: When a
-multicast listener is available an IGMP packet of type
-ICMPV6_MGM_REDUCTION may be sent out. When reaching
-ip6_finish_output2(), if no neighbor entry for the target
-address is found, __neigh_create() is called with &nd_tbl,
-which it'll want to lock.
-
-Move the elements into their own list, then unlock the table
-and perform the destruction.
-
-Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199289
-Fixes: 6fd6ce2056de ("ipv6: Do not depend on rt->n in ip6_finish_output2().")
-Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
----
- net/core/neighbour.c | 28 ++++++++++++++++++----------
- 1 file changed, 18 insertions(+), 10 deletions(-)
-
-diff --git a/net/core/neighbour.c b/net/core/neighbour.c
-index 7f831711b6e0..ff6c491d92ac 100644
---- a/net/core/neighbour.c
-+++ b/net/core/neighbour.c
-@@ -55,7 +55,8 @@ static void neigh_timer_handler(struct timer_list *t);
- static void __neigh_notify(struct neighbour *n, int type, int flags,
- u32 pid);
- static void neigh_update_notify(struct neighbour *neigh, u32 nlmsg_pid);
--static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev);
-+static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
-+ struct net_device *dev);
-
- #ifdef CONFIG_PROC_FS
- static const struct file_operations neigh_stat_seq_fops;
-@@ -291,8 +292,7 @@ int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
- {
- write_lock_bh(&tbl->lock);
- neigh_flush_dev(tbl, dev);
-- pneigh_ifdown(tbl, dev);
-- write_unlock_bh(&tbl->lock);
-+ pneigh_ifdown_and_unlock(tbl, dev);
-
- del_timer_sync(&tbl->proxy_timer);
- pneigh_queue_purge(&tbl->proxy_queue);
-@@ -681,9 +681,10 @@ int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *pkey,
- return -ENOENT;
- }
-
--static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
-+static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
-+ struct net_device *dev)
- {
-- struct pneigh_entry *n, **np;
-+ struct pneigh_entry *n, **np, *freelist = NULL;
- u32 h;
-
- for (h = 0; h <= PNEIGH_HASHMASK; h++) {
-@@ -691,16 +692,23 @@ static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
- while ((n = *np) != NULL) {
- if (!dev || n->dev == dev) {
- *np = n->next;
-- if (tbl->pdestructor)
-- tbl->pdestructor(n);
-- if (n->dev)
-- dev_put(n->dev);
-- kfree(n);
-+ n->next = freelist;
-+ freelist = n;
- continue;
- }
- np = &n->next;
- }
- }
-+ write_unlock_bh(&tbl->lock);
-+ while ((n = freelist)) {
-+ freelist = n->next;
-+ n->next = NULL;
-+ if (tbl->pdestructor)
-+ tbl->pdestructor(n);
-+ if (n->dev)
-+ dev_put(n->dev);
-+ kfree(n);
-+ }
- return -ENOENT;
- }
-
---
-2.14.2
-