netdev - [PATCH net] net: ipv4: fix one memleak in __inet_del

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Date: Tue, 5 Sep 2023 21:55:54 +0800
From: Liu Jian <liujian56@...wei.com>
To: <davem@...emloft.net>, <dsahern@...nel.org>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <hadi@...erus.ca>,
	<netdev@...r.kernel.org>
CC: <liujian56@...wei.com>
Subject: [PATCH net] net: ipv4: fix one memleak in __inet_del_ifa()

I got the below warning when do fuzzing test:
unregister_netdevice: waiting for bond0 to become free. Usage count = 2

It can be repoduced via:

ip link add bond0 type bond
sysctl -w net.ipv4.conf.bond0.promote_secondaries=1
ip addr add 4.117.174.103/0 scope 0x40 dev bond0
ip addr add 192.168.100.111/255.255.255.254 scope 0 dev bond0
ip addr add 0.0.0.4/0 scope 0x40 secondary dev bond0
ip addr del 4.117.174.103/0 scope 0x40 dev bond0
ip link delete bond0 type bond

In this reproduction test case, an incorrect 'last_prim' is found in
__inet_del_ifa(), as a result, the secondary address(0.0.0.4/0 scope 0x40)
is lost. The memory of the secondary address is leaked and the reference of
in_device and net_device is leaked.

Fix this problem by modifying the PROMOTE_SECONDANCE behavior as follows:
1. Traverse in_dev->ifa_list to search for the actual 'last_prim'.
2. When last_prim is empty, move 'promote' to the in_dev->ifa_list header.

Fixes: 0ff60a45678e ("[IPV4]: Fix secondary IP addresses after promotion")
Signed-off-by: Liu Jian <liujian56@...wei.com>
---
 net/ipv4/devinet.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 9cf64ee47dd2..99278f4b58e0 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -355,14 +355,13 @@ static void __inet_del_ifa(struct in_device *in_dev,
 {
 	struct in_ifaddr *promote = NULL;
 	struct in_ifaddr *ifa, *ifa1;
-	struct in_ifaddr *last_prim;
+	struct in_ifaddr *last_prim = NULL;
 	struct in_ifaddr *prev_prom = NULL;
 	int do_promote = IN_DEV_PROMOTE_SECONDARIES(in_dev);
 
 	ASSERT_RTNL();
 
 	ifa1 = rtnl_dereference(*ifap);
-	last_prim = rtnl_dereference(in_dev->ifa_list);
 	if (in_dev->dead)
 		goto no_promotions;
 
@@ -371,7 +370,16 @@ static void __inet_del_ifa(struct in_device *in_dev,
 	 **/
 
 	if (!(ifa1->ifa_flags & IFA_F_SECONDARY)) {
-		struct in_ifaddr __rcu **ifap1 = &ifa1->ifa_next;
+		struct in_ifaddr __rcu **ifap1 = &in_dev->ifa_list;
+
+		while ((ifa = rtnl_dereference(*ifap1)) != NULL) {
+			if (ifa1 == ifa)
+				break;
+			last_prim = ifa;
+			ifap1 = &ifa->ifa_next;
+		}
+
+		ifap1 = &ifa1->ifa_next;
 
 		while ((ifa = rtnl_dereference(*ifap1)) != NULL) {
 			if (!(ifa->ifa_flags & IFA_F_SECONDARY) &&
@@ -440,9 +448,15 @@ static void __inet_del_ifa(struct in_device *in_dev,
 
 			rcu_assign_pointer(prev_prom->ifa_next, next_sec);
 
-			last_sec = rtnl_dereference(last_prim->ifa_next);
-			rcu_assign_pointer(promote->ifa_next, last_sec);
-			rcu_assign_pointer(last_prim->ifa_next, promote);
+			if (last_prim) {
+				last_sec = rtnl_dereference(last_prim->ifa_next);
+				rcu_assign_pointer(promote->ifa_next, last_sec);
+				rcu_assign_pointer(last_prim->ifa_next, promote);
+			} else {
+				rcu_assign_pointer(promote->ifa_next,
+						   rtnl_dereference(in_dev->ifa_list));
+				rcu_assign_pointer(in_dev->ifa_list, promote);
+			}
 		}
 
 		promote->ifa_flags &= ~IFA_F_SECONDARY;
-- 
2.34.1