[PATCH net v2] net: ipv4: devinet: Fix crash when add/del multicast IP with autojoin

[PATCH net v2] net: ipv4: devinet: Fix crash when add/del multicast IP with autojoin

[Vadym Kochan]

From: Taras Chornyi <taras.chornyi@plvision.eu>

When CONFIG_IP_MULTICAST is not set and multicast ip is added to the device
with autojoin flag or when multicast ip is deleted kernel will crash.

steps to reproduce:

ip addr add 224.0.0.0/32 dev eth0
ip addr del 224.0.0.0/32 dev eth0

or

ip addr add 224.0.0.0/32 dev eth0 autojoin

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000088
 pc : _raw_write_lock_irqsave+0x1e0/0x2ac
 lr : lock_sock_nested+0x1c/0x60
 Call trace:
  _raw_write_lock_irqsave+0x1e0/0x2ac
  lock_sock_nested+0x1c/0x60
  ip_mc_config.isra.28+0x50/0xe0
  inet_rtm_deladdr+0x1a8/0x1f0
  rtnetlink_rcv_msg+0x120/0x350
  netlink_rcv_skb+0x58/0x120
  rtnetlink_rcv+0x14/0x20
  netlink_unicast+0x1b8/0x270
  netlink_sendmsg+0x1a0/0x3b0
  ____sys_sendmsg+0x248/0x290
  ___sys_sendmsg+0x80/0xc0
  __sys_sendmsg+0x68/0xc0
  __arm64_sys_sendmsg+0x20/0x30
  el0_svc_common.constprop.2+0x88/0x150
  do_el0_svc+0x20/0x80
 el0_sync_handler+0x118/0x190
  el0_sync+0x140/0x180

Fixes: 93a714d (multicast: Extend ip address command to enable multicast group join/leave on)
Signed-off-by: Taras Chornyi <taras.chornyi@plvision.eu>
Signed-off-by: Vadym Kochan <vadym.kochan@plvision.eu>
---

v2:
    Fixed type "reptoduse" -> "reproduce" in commit message.

 net/ipv4/devinet.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 30fa42f5997d..c0dd561aa190 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -614,12 +614,15 @@ struct in_ifaddr *inet_ifa_byprefix(struct in_device *in_dev, __be32 prefix,
 	return NULL;
 }
 
-static int ip_mc_config(struct sock *sk, bool join, const struct in_ifaddr *ifa)
+static int ip_mc_autojoin_config(struct net *net, bool join,
+				 const struct in_ifaddr *ifa)
 {
+#if defined(CONFIG_IP_MULTICAST)
 	struct ip_mreqn mreq = {
 		.imr_multiaddr.s_addr = ifa->ifa_address,
 		.imr_ifindex = ifa->ifa_dev->dev->ifindex,
 	};
+	struct sock *sk = net->ipv4.mc_autojoin_sk;
 	int ret;
 
 	ASSERT_RTNL();
@@ -632,6 +635,9 @@ static int ip_mc_config(struct sock *sk, bool join, const struct in_ifaddr *ifa)
 	release_sock(sk);
 
 	return ret;
+#else
+	return -EOPNOTSUPP;
+#endif
 }
 
 static int inet_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh,
@@ -675,7 +681,7 @@ static int inet_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh,
 			continue;
 
 		if (ipv4_is_multicast(ifa->ifa_address))
-			ip_mc_config(net->ipv4.mc_autojoin_sk, false, ifa);
+			ip_mc_autojoin_config(net, false, ifa);
 		__inet_del_ifa(in_dev, ifap, 1, nlh, NETLINK_CB(skb).portid);
 		return 0;
 	}
@@ -940,8 +946,7 @@ static int inet_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 		 */
 		set_ifa_lifetime(ifa, valid_lft, prefered_lft);
 		if (ifa->ifa_flags & IFA_F_MCAUTOJOIN) {
-			int ret = ip_mc_config(net->ipv4.mc_autojoin_sk,
-					       true, ifa);
+			int ret = ip_mc_autojoin_config(net, true, ifa);
 
 			if (ret < 0) {
 				inet_free_ifa(ifa);
-- 
2.17.1

Re: [PATCH net v2] net: ipv4: devinet: Fix crash when add/del multicast IP with autojoin

[David Miller]

From: Vadym Kochan <vadym.kochan@plvision.eu>
Date: Thu,  9 Apr 2020 08:39:32 +0300

> Fixes: 93a714d (multicast: Extend ip address command to enable multicast group join/leave on)

Fixes tags must specify commit IDs with 12 digits of significance.
Please fix this and resubmit.

And in the parenthesis, the commit header text should also be surrounded
by double quotes like ("...")