[PATCH nf-next v4 3/4] netfilter: nf_conntrack_amanda: use nf_ct_helper_parse_port()

[Rahul Chandelkar <rc@rexion.ai>]

amanda_help() passed the result of simple_strtoul() straight through
htons() into a __be16.  The digit string is copied into a 6-byte buffer,
so at most five digits are parsed, but values 65536-99999 still truncated
on the u16 conversion (e.g. 65537 became 1).

Use nf_ct_helper_parse_port(), which rejects port 0 and values above
65535 in one call.  The trailing len is still derived from the parser's
end pointer for the NAT mangle path.

Fixes: 16958900578b ("[NETFILTER]: nf_conntrack/nf_nat: add amanda helper port")
Signed-off-by: Rahul Chandelkar <rc@rexion.ai>
---
 net/netfilter/nf_conntrack_amanda.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_conntrack_amanda.c b/net/netfilter/nf_conntrack_amanda.c
index 14ae660491f3..f157c96b7d22 100644
--- a/net/netfilter/nf_conntrack_amanda.c
+++ b/net/netfilter/nf_conntrack_amanda.c
@@ -89,7 +89,7 @@ static int amanda_help(struct sk_buff *skb,
 	struct nf_conntrack_tuple *tuple;
 	unsigned int dataoff, start, stop, off, i;
 	char pbuf[sizeof("65535")], *tmp;
-	u16 len;
+	u16 len, parsed_port;
 	__be16 port;
 	int ret = NF_ACCEPT;
 	nf_nat_amanda_hook_fn *nf_nat_amanda;
@@ -132,10 +132,10 @@ static int amanda_help(struct sk_buff *skb,
 			break;
 		pbuf[len] = '\0';
 
-		port = htons(simple_strtoul(pbuf, &tmp, 10));
-		len = tmp - pbuf;
-		if (port == 0 || len > 5)
+		if (nf_ct_helper_parse_port(pbuf, len, &parsed_port, &tmp))
 			break;
+		port = htons(parsed_port);
+		len = tmp - pbuf;
 
 		exp = nf_ct_expect_alloc(ct);
 		if (exp == NULL) {
-- 
2.43.0