netdev - [PATCH v2 net-next 2/6] arp: Validate netmask earlier for SIOCDARP and SIOCSARP in arp

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Message-ID: <20240425170002.68160-3-kuniyu@amazon.com>
Date: Thu, 25 Apr 2024 09:59:58 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, "Paolo
 Abeni" <pabeni@...hat.com>
CC: Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
	<kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v2 net-next 2/6] arp: Validate netmask earlier for SIOCDARP and SIOCSARP in arp_ioctl().

When ioctl(SIOCDARP/SIOCSARP) is issued with ATF_PUBL, r.arp_netmask
must be 0.0.0.0 or 255.255.255.255.

Currently, the netmask is validated in arp_req_delete_public() or
arp_req_set_public() under rtnl_lock().

We have ATF_NETMASK test in arp_ioctl() before holding rtnl_lock(),
so let's move the netmask validation there.

Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/ipv4/arp.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 3093374165fa..b20a5771d069 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1023,11 +1023,8 @@ static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
 static int arp_req_set_public(struct net *net, struct arpreq *r,
 		struct net_device *dev)
 {
-	__be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
 	__be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
 
-	if (mask && mask != htonl(0xFFFFFFFF))
-		return -EINVAL;
 	if (!dev && (r->arp_flags & ATF_COM)) {
 		dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
 				      r->arp_ha.sa_data);
@@ -1035,6 +1032,8 @@ static int arp_req_set_public(struct net *net, struct arpreq *r,
 			return -ENODEV;
 	}
 	if (mask) {
+		__be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+
 		if (!pneigh_lookup(&arp_tbl, net, &ip, dev, 1))
 			return -ENOBUFS;
 		return 0;
@@ -1171,14 +1170,13 @@ int arp_invalidate(struct net_device *dev, __be32 ip, bool force)
 static int arp_req_delete_public(struct net *net, struct arpreq *r,
 		struct net_device *dev)
 {
-	__be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
 	__be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
 
-	if (mask == htonl(0xFFFFFFFF))
-		return pneigh_delete(&arp_tbl, net, &ip, dev);
+	if (mask) {
+		__be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
 
-	if (mask)
-		return -EINVAL;
+		return pneigh_delete(&arp_tbl, net, &ip, dev);
+	}
 
 	return arp_req_set_proxy(net, dev, 0);
 }
@@ -1211,9 +1209,10 @@ static int arp_req_delete(struct net *net, struct arpreq *r,
 
 int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
 {
-	int err;
-	struct arpreq r;
 	struct net_device *dev = NULL;
+	struct arpreq r;
+	__be32 *netmask;
+	int err;
 
 	switch (cmd) {
 	case SIOCDARP:
@@ -1236,9 +1235,13 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
 	if (!(r.arp_flags & ATF_PUBL) &&
 	    (r.arp_flags & (ATF_NETMASK | ATF_DONTPUB)))
 		return -EINVAL;
+
+	netmask = &((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr;
 	if (!(r.arp_flags & ATF_NETMASK))
-		((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
-							   htonl(0xFFFFFFFFUL);
+		*netmask = htonl(0xFFFFFFFFUL);
+	else if (*netmask && *netmask != htonl(0xFFFFFFFFUL))
+		return -EINVAL;
+
 	rtnl_lock();
 	if (r.arp_dev[0]) {
 		err = -ENODEV;
-- 
2.30.2