[PATCH net-next 2/2] netfilter: nf_conntrack_amanda: reject port values above 65535

[HACKE-RC <rc@rexion.ai>]

amanda_help() converts the result of simple_strtoul() to __be16 via
htons() without checking the parsed value fits in 16 bits. The
existing len > 5 guard limits strings to five digits, capping the
parseable range at 99999, but values 65536-99999 still silently
truncate on the htons() conversion.

Use an intermediate unsigned long and reject out-of-range values
before converting to network byte order.

Fixes: 16958900578b ("[NETFILTER]: nf_conntrack/nf_nat: add amanda helper port")
Signed-off-by: HACKE-RC <rc@rexion.ai>
---
 net/netfilter/nf_conntrack_amanda.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_conntrack_amanda.c b/net/netfilter/nf_conntrack_amanda.c
index d2c09e8dd..58d6c9f29 100644
--- a/net/netfilter/nf_conntrack_amanda.c
+++ b/net/netfilter/nf_conntrack_amanda.c
@@ -88,11 +88,12 @@ static int amanda_help(struct sk_buff *skb,
 	struct nf_conntrack_expect *exp;
 	struct nf_conntrack_tuple *tuple;
 	unsigned int dataoff, start, stop, off, i;
+	nf_nat_amanda_hook_fn *nf_nat_amanda;
 	char pbuf[sizeof("65535")], *tmp;
+	unsigned long parsed_port;
+	int ret = NF_ACCEPT;
 	u_int16_t len;
 	__be16 port;
-	int ret = NF_ACCEPT;
-	nf_nat_amanda_hook_fn *nf_nat_amanda;
 
 	/* Only look at packets from the Amanda server */
 	if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
@@ -132,10 +133,11 @@ static int amanda_help(struct sk_buff *skb,
 			break;
 		pbuf[len] = '\0';
 
-		port = htons(simple_strtoul(pbuf, &tmp, 10));
+		parsed_port = simple_strtoul(pbuf, &tmp, 10);
 		len = tmp - pbuf;
-		if (port == 0 || len > 5)
+		if (parsed_port == 0 || parsed_port > 65535 || len > 5)
 			break;
+		port = htons(parsed_port);
 
 		exp = nf_ct_expect_alloc(ct);
 		if (exp == NULL) {
-- 
2.54.0