[PATCH v2 1/2] RDMA/rxe: Fix null-ptr-deref in kernel_sock_shutdown().

[Kuniyuki Iwashima <kuniyu@google.com>]

syzbot reported null-ptr-deref in kernel_sock_shutdown(). [0]

The problem is ->newlink() and ->dellink() can be called
concurrently with no synchronisation, leading sk leak or
double free, etc.

We defer UDP tunnel allocation to the first device creation,
but this would requrie per-netns locking.

Let's allocate UDP tunnels in the __init_net hook.

Now extra sock_hold() and __sock_put() are no longer needed.

Note that rxe_ns_pernet_sk6() is broken and will be fixed
in the following patch.

[0]:
Oops: general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 3 UID: 0 PID: 12652 Comm: syz.7.1709 Tainted: G             L      syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:kernel_sock_shutdown+0x47/0x70 net/socket.c:3785
Code: fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 33 48 b8 00 00 00 00 00 fc ff df 4c 8b 63 20 49 8d 7c 24 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 1a 49 8b 44 24 68 89 ee 48 89 df 5b 5d 41 5c e9 46
RSP: 0018:ffffc9000566f180 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff888058587240 RCX: 0000000000000000
RDX: 000000000000000d RSI: ffffffff895ced12 RDI: 0000000000000068
RBP: 0000000000000002 R08: 0000000000000001 R09: ffffed1006d98945
R10: ffff888036cc4a2b R11: 0000003683c25c00 R12: 0000000000000000
R13: ffff88805c998000 R14: 0000000000000002 R15: 0000000000000018
FS:  00007f1306d976c0(0000) GS:ffff8880d65db000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1306d97d58 CR3: 00000000404f1000 CR4: 0000000000352ef0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000002
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 udp_tunnel_sock_release+0x68/0x80 net/ipv4/udp_tunnel_core.c:202
 rxe_release_udp_tunnel drivers/infiniband/sw/rxe/rxe_net.c:294 [inline]
 rxe_sock_put+0xae/0x130 drivers/infiniband/sw/rxe/rxe_net.c:639
 rxe_net_del+0x83/0x120 drivers/infiniband/sw/rxe/rxe_net.c:660
 rxe_dellink+0x15/0x20 drivers/infiniband/sw/rxe/rxe.c:254
 nldev_dellink+0x289/0x3c0 drivers/infiniband/core/nldev.c:1849
 rdma_nl_rcv_msg+0x392/0x6f0 drivers/infiniband/core/netlink.c:195
 rdma_nl_rcv_skb.constprop.0.isra.0+0x2cb/0x410 drivers/infiniband/core/netlink.c:239
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 ____sys_sendmsg+0x9e1/0xb70 net/socket.c:2698
 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2752
 __sys_sendmsg+0x170/0x220 net/socket.c:2784
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1305f9c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1306d97028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f1306216090 RCX: 00007f1305f9c819
RDX: 0000000000000000 RSI: 00002000000002c0 RDI: 0000000000000003
RBP: 00007f1306032c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1306216128 R14: 00007f1306216090 R15: 00007ffd8ecad288
 </TASK>
Modules linked in:

Fixes: f1327abd6abe ("RDMA/rxe: Support RDMA link creation and destruction per net namespace")
Reported-by: syzbot+d8f76778263ab65c2b21@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69ea344f.a00a0220.17a17.0040.GAE@google.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
v2: Set up UDP tunnels in __net_init instead of adding mutex.
v1: https://lore.kernel.org/all/20260424013759.728288-1-kuniyu@google.com/
---
 drivers/infiniband/sw/rxe/rxe.c     |   6 --
 drivers/infiniband/sw/rxe/rxe_net.c | 126 ++--------------------------
 drivers/infiniband/sw/rxe/rxe_net.h |   5 +-
 drivers/infiniband/sw/rxe/rxe_ns.c  |  90 +++++++++-----------
 drivers/infiniband/sw/rxe/rxe_ns.h  |   1 -
 5 files changed, 47 insertions(+), 181 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe.c b/drivers/infiniband/sw/rxe/rxe.c
index b0714f9abe3d..111ba4e57261 100644
--- a/drivers/infiniband/sw/rxe/rxe.c
+++ b/drivers/infiniband/sw/rxe/rxe.c
@@ -236,10 +236,6 @@ static int rxe_newlink(const char *ibdev_name, struct net_device *ndev)
 		goto err;
 	}
 
-	err = rxe_net_init(ndev);
-	if (err)
-		return err;
-
 	err = rxe_net_add(ibdev_name, ndev);
 	if (err) {
 		rxe_err("failed to add %s\n", ndev->name);
@@ -251,8 +247,6 @@ static int rxe_newlink(const char *ibdev_name, struct net_device *ndev)
 
 static int rxe_dellink(struct ib_device *dev)
 {
-	rxe_net_del(dev);
-
 	return 0;
 }
 
diff --git a/drivers/infiniband/sw/rxe/rxe_net.c b/drivers/infiniband/sw/rxe/rxe_net.c
index 50a2cb5405e2..9080d4c893a1 100644
--- a/drivers/infiniband/sw/rxe/rxe_net.c
+++ b/drivers/infiniband/sw/rxe/rxe_net.c
@@ -256,8 +256,8 @@ static int rxe_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	return 0;
 }
 
-static struct socket *rxe_setup_udp_tunnel(struct net *net, __be16 port,
-					   bool ipv6)
+struct sock *rxe_setup_udp_tunnel(struct net *net, __be16 port,
+				  bool ipv6)
 {
 	int err;
 	struct socket *sock;
@@ -285,13 +285,12 @@ static struct socket *rxe_setup_udp_tunnel(struct net *net, __be16 port,
 	/* Setup UDP tunnel */
 	setup_udp_tunnel_sock(net, sock, &tnl_cfg);
 
-	return sock;
+	return sock->sk;
 }
 
-static void rxe_release_udp_tunnel(struct socket *sk)
+void rxe_release_udp_tunnel(struct sock *sk)
 {
-	if (sk)
-		udp_tunnel_sock_release(sk);
+	udp_tunnel_sock_release(sk->sk_socket);
 }
 
 static void prepare_udp_hdr(struct sk_buff *skb, __be16 src_port,
@@ -629,43 +628,6 @@ int rxe_net_add(const char *ibdev_name, struct net_device *ndev)
 	return 0;
 }
 
-static void rxe_sock_put(struct sock *sk,
-					void (*set_sk)(struct net *, struct sock *),
-					struct net *net)
-{
-	if (refcount_read(&sk->sk_refcnt) > SK_REF_FOR_TUNNEL) {
-		__sock_put(sk);
-	} else {
-		rxe_release_udp_tunnel(sk->sk_socket);
-		sk = NULL;
-		set_sk(net, sk);
-	}
-}
-
-void rxe_net_del(struct ib_device *dev)
-{
-	struct rxe_dev *rxe = container_of(dev, struct rxe_dev, ib_dev);
-	struct net_device *ndev;
-	struct sock *sk;
-	struct net *net;
-
-	ndev = rxe_ib_device_get_netdev(&rxe->ib_dev);
-	if (!ndev)
-		return;
-
-	net = dev_net(ndev);
-
-	sk = rxe_ns_pernet_sk4(net);
-	if (sk)
-		rxe_sock_put(sk, rxe_ns_pernet_set_sk4, net);
-
-	sk = rxe_ns_pernet_sk6(net);
-	if (sk)
-		rxe_sock_put(sk, rxe_ns_pernet_set_sk6, net);
-
-	dev_put(ndev);
-}
-
 static void rxe_port_event(struct rxe_dev *rxe,
 			   enum ib_event_type event)
 {
@@ -722,7 +684,6 @@ static int rxe_notify(struct notifier_block *not_blk,
 	switch (event) {
 	case NETDEV_UNREGISTER:
 		ib_unregister_device_queued(&rxe->ib_dev);
-		rxe_net_del(&rxe->ib_dev);
 		break;
 	case NETDEV_CHANGEMTU:
 		rxe_dbg_dev(rxe, "%s changed mtu to %d\n", ndev->name, ndev->mtu);
@@ -752,56 +713,6 @@ static struct notifier_block rxe_net_notifier = {
 	.notifier_call = rxe_notify,
 };
 
-static int rxe_net_ipv4_init(struct net *net)
-{
-	struct sock *sk;
-	struct socket *sock;
-
-	sk = rxe_ns_pernet_sk4(net);
-	if (sk) {
-		sock_hold(sk);
-		return 0;
-	}
-
-	sock = rxe_setup_udp_tunnel(net, htons(ROCE_V2_UDP_DPORT), false);
-	if (IS_ERR(sock)) {
-		pr_err("Failed to create IPv4 UDP tunnel\n");
-		return -1;
-	}
-	rxe_ns_pernet_set_sk4(net, sock->sk);
-
-	return 0;
-}
-
-static int rxe_net_ipv6_init(struct net *net)
-{
-#if IS_ENABLED(CONFIG_IPV6)
-	struct sock *sk;
-	struct socket *sock;
-
-	sk = rxe_ns_pernet_sk6(net);
-	if (sk) {
-		sock_hold(sk);
-		return 0;
-	}
-
-	sock = rxe_setup_udp_tunnel(net, htons(ROCE_V2_UDP_DPORT), true);
-	if (PTR_ERR(sock) == -EAFNOSUPPORT) {
-		pr_warn("IPv6 is not supported, can not create a UDPv6 socket\n");
-		return 0;
-	}
-
-	if (IS_ERR(sock)) {
-		pr_err("Failed to create IPv6 UDP tunnel\n");
-		return -1;
-	}
-
-	rxe_ns_pernet_set_sk6(net, sock->sk);
-
-#endif
-	return 0;
-}
-
 int rxe_register_notifier(void)
 {
 	int err;
@@ -819,30 +730,3 @@ void rxe_net_exit(void)
 {
 	unregister_netdevice_notifier(&rxe_net_notifier);
 }
-
-int rxe_net_init(struct net_device *ndev)
-{
-	struct net *net;
-	struct sock *sk;
-	int err;
-
-	net = dev_net(ndev);
-
-	err = rxe_net_ipv4_init(net);
-	if (err)
-		return err;
-
-	err = rxe_net_ipv6_init(net);
-	if (err)
-		goto err_out;
-
-	return 0;
-
-err_out:
-	/* If ipv6 error, release ipv4 resource */
-	sk = rxe_ns_pernet_sk4(net);
-	if (sk)
-		rxe_sock_put(sk, rxe_ns_pernet_set_sk4, net);
-
-	return err;
-}
diff --git a/drivers/infiniband/sw/rxe/rxe_net.h b/drivers/infiniband/sw/rxe/rxe_net.h
index 56249677d692..592b0e577f32 100644
--- a/drivers/infiniband/sw/rxe/rxe_net.h
+++ b/drivers/infiniband/sw/rxe/rxe_net.h
@@ -11,11 +11,12 @@
 #include <net/if_inet6.h>
 #include <linux/module.h>
 
+struct sock *rxe_setup_udp_tunnel(struct net *net, __be16 port, bool ipv6);
+void rxe_release_udp_tunnel(struct sock *sk);
+
 int rxe_net_add(const char *ibdev_name, struct net_device *ndev);
-void rxe_net_del(struct ib_device *dev);
 
 int rxe_register_notifier(void);
-int rxe_net_init(struct net_device *ndev);
 void rxe_net_exit(void);
 
 #endif /* RXE_NET_H */
diff --git a/drivers/infiniband/sw/rxe/rxe_ns.c b/drivers/infiniband/sw/rxe/rxe_ns.c
index 8b9d734229b2..06eb2e2387a1 100644
--- a/drivers/infiniband/sw/rxe/rxe_ns.c
+++ b/drivers/infiniband/sw/rxe/rxe_ns.c
@@ -7,8 +7,10 @@
 #include <linux/skbuff.h>
 #include <linux/pid_namespace.h>
 #include <net/udp_tunnel.h>
+#include <rdma/ib_verbs.h>
 
 #include "rxe_ns.h"
+#include "rxe_net.h"
 
 /*
  * Per network namespace data
@@ -23,40 +25,54 @@ struct rxe_ns_sock {
  */
 static unsigned int rxe_pernet_id;
 
-/*
- * Called for every existing and added network namespaces
- */
-static int rxe_ns_init(struct net *net)
+static __net_init int rxe_ns_init(struct net *net)
 {
-	/* defer socket create in the namespace to the first
-	 * device create.
-	 */
+	struct rxe_ns_sock *ns_sk = net_generic(net, rxe_pernet_id);
+	struct sock *sk;
+	int err = 0;
+
+	sk = rxe_setup_udp_tunnel(net, htons(ROCE_V2_UDP_DPORT), false);
+	if (IS_ERR(sk)) {
+		err = PTR_ERR(sk);
+		goto out;
+	}
+
+	RCU_INIT_POINTER(ns_sk->rxe_sk4, sk);
+
+#if IS_ENABLED(CONFIG_IPV6)
+	sk = rxe_setup_udp_tunnel(net, htons(ROCE_V2_UDP_DPORT), true);
+	if (IS_ERR(sk)) {
+		err = PTR_ERR(sk);
+		if (err == -EAFNOSUPPORT) {
+			err = 0;
+			goto out;
+		}
+
+		sk = rcu_dereference_protected(ns_sk->rxe_sk4, 1);
+		rxe_release_udp_tunnel(sk);
+		goto out;
+	}
 
-	return 0;
+	RCU_INIT_POINTER(ns_sk->rxe_sk6, sk);
+#endif
+out:
+	return err;
 }
 
-static void rxe_ns_exit(struct net *net)
+static __net_exit void rxe_ns_exit(struct net *net)
 {
-	/* called when the network namespace is removed
-	 */
 	struct rxe_ns_sock *ns_sk = net_generic(net, rxe_pernet_id);
 	struct sock *sk;
 
-	rcu_read_lock();
-	sk = rcu_dereference(ns_sk->rxe_sk4);
-	rcu_read_unlock();
-	if (sk) {
-		rcu_assign_pointer(ns_sk->rxe_sk4, NULL);
-		udp_tunnel_sock_release(sk->sk_socket);
-	}
+	sk = rcu_dereference_protected(ns_sk->rxe_sk4, 1);
+	RCU_INIT_POINTER(ns_sk->rxe_sk4, NULL);
+	rxe_release_udp_tunnel(sk);
 
 #if IS_ENABLED(CONFIG_IPV6)
-	rcu_read_lock();
-	sk = rcu_dereference(ns_sk->rxe_sk6);
-	rcu_read_unlock();
+	sk = rcu_dereference_protected(ns_sk->rxe_sk6, 1);
 	if (sk) {
-		rcu_assign_pointer(ns_sk->rxe_sk6, NULL);
-		udp_tunnel_sock_release(sk->sk_socket);
+		RCU_INIT_POINTER(ns_sk->rxe_sk6, NULL);
+		rxe_release_udp_tunnel(sk);
 	}
 #endif
 }
@@ -71,26 +87,6 @@ static struct pernet_operations rxe_net_ops = {
 	.size = sizeof(struct rxe_ns_sock),
 };
 
-struct sock *rxe_ns_pernet_sk4(struct net *net)
-{
-	struct rxe_ns_sock *ns_sk = net_generic(net, rxe_pernet_id);
-	struct sock *sk;
-
-	rcu_read_lock();
-	sk = rcu_dereference(ns_sk->rxe_sk4);
-	rcu_read_unlock();
-
-	return sk;
-}
-
-void rxe_ns_pernet_set_sk4(struct net *net, struct sock *sk)
-{
-	struct rxe_ns_sock *ns_sk = net_generic(net, rxe_pernet_id);
-
-	rcu_assign_pointer(ns_sk->rxe_sk4, sk);
-	synchronize_rcu();
-}
-
 #if IS_ENABLED(CONFIG_IPV6)
 struct sock *rxe_ns_pernet_sk6(struct net *net)
 {
@@ -103,14 +99,6 @@ struct sock *rxe_ns_pernet_sk6(struct net *net)
 
 	return sk;
 }
-
-void rxe_ns_pernet_set_sk6(struct net *net, struct sock *sk)
-{
-	struct rxe_ns_sock *ns_sk = net_generic(net, rxe_pernet_id);
-
-	rcu_assign_pointer(ns_sk->rxe_sk6, sk);
-	synchronize_rcu();
-}
 #endif /* IPV6 */
 
 int rxe_namespace_init(void)
diff --git a/drivers/infiniband/sw/rxe/rxe_ns.h b/drivers/infiniband/sw/rxe/rxe_ns.h
index 4da2709e6b71..7f48d624fa05 100644
--- a/drivers/infiniband/sw/rxe/rxe_ns.h
+++ b/drivers/infiniband/sw/rxe/rxe_ns.h
@@ -3,7 +3,6 @@
 #ifndef RXE_NS_H
 #define RXE_NS_H
 
-struct sock *rxe_ns_pernet_sk4(struct net *net);
 void rxe_ns_pernet_set_sk4(struct net *net, struct sock *sk);
 
 #if IS_ENABLED(CONFIG_IPV6)
-- 
2.54.0.rc2.544.gc7ae2d5bb8-goog