net/x25: fix called/calling length calculation in x25_parse_address_block

BugLink: https://bugs.launchpad.net/bugs/1858489

[ Upstream commit d449ba3d ]

The length of the called and calling address was not calculated
correctly (BCD encoding).
Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/x25/af_x25.c

@@ -100,7 +100,7 @@ int x25_parse_address_block(struct sk_buff *skb,
 	}
 
 	len = *skb->data;
-	needed = 1 + (len >> 4) + (len & 0x0f);
+	needed = 1 + ((len >> 4) + (len & 0x0f) + 1) / 2;
 
 	if (!pskb_may_pull(skb, needed)) {
 		/* packet is too short to hold the addresses it claims