Commit 8cc196d6 authored Dec 10, 2018 by David Ahern Committed by David S. Miller Dec 10, 2018

neighbor: gc_list changes should be protected by table lock



Adding and removing neighbor entries to / from the gc_list need to be
done while holding the table lock; a couple of places were missed in the
original patch.

Move the list_add_tail in neigh_alloc to ___neigh_create where the lock
is already obtained. Since neighbor entries should rarely be moved
to/from PERMANENT state, add lock/unlock around the gc_list changes in
neigh_change_state rather than extending the lock hold around all
neighbor updates.

Fixes: 58956317 ("neighbor: Improve garbage collection")
Reported-by: Andrei Vagin <avagin@gmail.com>
Reported-by:  <syzbot+6cc2fd1d3bdd2e007363@syzkaller.appspotmail.com>
Reported-by:  <syzbot+35e87b87c00f386b041f@syzkaller.appspotmail.com>
Reported-by:  <syzbot+b354d1fb59091ea73c37@syzkaller.appspotmail.com>
Reported-by:  <syzbot+3ddead5619658537909b@syzkaller.appspotmail.com>
Reported-by:  <syzbot+424d47d5c456ce8b2bbe@syzkaller.appspotmail.com>
Reported-by:  <syzbot+e4d42eb35f6a27b0a628@syzkaller.appspotmail.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 93698321

net/core/neighbour.c

+10 −5

Original line number	Diff line number	Diff line
		@@ -138,11 +138,17 @@ static void neigh_change_state(struct neighbour *n, u8 new)
		* add to the gc list if new state is not permanent
		*/
		if (new_is_perm && on_gc_list) {
		write_lock_bh(&n->tbl->lock);
		list_del_init(&n->gc_list);
		write_unlock_bh(&n->tbl->lock);

		atomic_dec(&n->tbl->gc_entries);
		} else if (!new_is_perm && !on_gc_list) {
		/* add entries to the tail; cleaning removes from the front */
		write_lock_bh(&n->tbl->lock);
		list_add_tail(&n->gc_list, &n->tbl->gc_list);
		write_unlock_bh(&n->tbl->lock);

		atomic_inc(&n->tbl->gc_entries);
		}
		}
		@@ -390,10 +396,6 @@ do_alloc:
		n->tbl = tbl;
		refcount_set(&n->refcnt, 1);
		n->dead = 1;

		if (!permanent)
		list_add_tail(&n->gc_list, &n->tbl->gc_list);
		else
		INIT_LIST_HEAD(&n->gc_list);

		atomic_inc(&tbl->entries);
		@@ -616,6 +618,9 @@ static struct neighbour ___neigh_create(struct neigh_table tbl,
		}

		n->dead = 0;
		if (!permanent)
		list_add_tail(&n->gc_list, &n->tbl->gc_list);

		if (want_ref)
		neigh_hold(n);
		rcu_assign_pointer(n->next,

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