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Commit 53b76cdf authored by Wolfgang Bumiller's avatar Wolfgang Bumiller Committed by David S. Miller
Browse files

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: 6fd6ce20 ("ipv6: Do not depend on rt->n in ip6_finish_output2().")
Signed-off-by: default avatarWolfgang Bumiller <w.bumiller@proxmox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1071ec9d

net/core/neighbour.c

+18 −10
Original line number Diff line number Diff line
@@ -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++) {
@@ -691,15 +692,22 @@ static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev) 
		while ((n = *np) != NULL) {

			if (!dev || n->dev == dev) {

				*np = n->next;

				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);

				continue;

			}

			np = &n->next;

		}

	}

	return -ENOENT;

}