netfilter: synproxy: synproxy_cpu_seq_next should increase position index

stable inclusion
from linux-4.19.111
commit 4fbcbed7c45189b5f7f3309aaed8fc81c37e9bba

--------------------------------

commit bb71f846 upstream.

If .next function does not change position index,
following .show function will repeat output related
to current position index.

Cc: stable@vger.kernel.org
Fixes: 1f4aace6 ("fs/seq_file.c: simplify seq_file iteration code ...")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206283Signed-off-by: NVasily Averin <vvs@virtuozzo.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NLi Aichun <liaichun@huawei.com>
Reviewed-by: Nguodeqing <geffrey.guo@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/netfilter/nf_synproxy_core.c

@@ -273,7 +273,7 @@ static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 		*pos = cpu + 1;
 		return per_cpu_ptr(snet->stats, cpu);
 	}
-
+	(*pos)++;
 	return NULL;
 }