Commit 64c6f4bb authored May 01, 2019 by David Ahern Committed by David S. Miller May 04, 2019

neighbor: Reset gc_entries counter if new entry is released before insert



Ian and Alan both reported seeing overflows after upgrades to 5.x kernels:
  neighbour: arp_cache: neighbor table overflow!

Alan's mpls script helped get to the bottom of this bug. When a new entry
is created the gc_entries counter is bumped in neigh_alloc to check if a
new one is allowed to be created. ___neigh_create then searches for an
existing entry before inserting the just allocated one. If an entry
already exists, the new one is dropped in favor of the existing one. In
this case the cleanup path needs to drop the gc_entries counter. There
is no memory leak, only a counter leak.

Fixes: 58956317 ("neighbor: Improve garbage collection")
Reported-by: Ian Kumlien <ian.kumlien@gmail.com>
Reported-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f0c5bcf2

net/core/neighbour.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -663,6 +663,8 @@ out:
		out_tbl_unlock:
		write_unlock_bh(&tbl->lock);
		out_neigh_release:
		if (!exempt_from_gc)
		atomic_dec(&tbl->gc_entries);
		neigh_release(n);
		goto out;
		}

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