neigh_stat_seq_next() should increase position index

[ Upstream commit 1e3f9f073c47bee7c23e77316b07bc12338c5bba ]

if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.

https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/core/neighbour.c

@@ -2797,6 +2797,7 @@ static void *neigh_stat_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 		*pos = cpu+1;
 		return per_cpu_ptr(tbl->stats, cpu);
 	}
+	(*pos)++;
 	return NULL;
 }