[PATCH] 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 rxe_net_del() can be called for the same
device concurrently.

Multiple threads might call udp_tunnel_sock_release()
for the same socket.

Let's add a per-netns mutex to synchronise rxe_net_del().

[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>
---
 drivers/infiniband/sw/rxe/rxe_net.c |  2 ++
 drivers/infiniband/sw/rxe/rxe_ns.c  | 18 ++++++++++++++++++
 drivers/infiniband/sw/rxe/rxe_ns.h  |  2 ++
 3 files changed, 22 insertions(+)

diff --git a/drivers/infiniband/sw/rxe/rxe_net.c b/drivers/infiniband/sw/rxe/rxe_net.c
index 50a2cb5405e2..1b3615c9262a 100644
--- a/drivers/infiniband/sw/rxe/rxe_net.c
+++ b/drivers/infiniband/sw/rxe/rxe_net.c
@@ -655,6 +655,7 @@ void rxe_net_del(struct ib_device *dev)
 
 	net = dev_net(ndev);
 
+	rxe_ns_pernet_sk_lock(net);
 	sk = rxe_ns_pernet_sk4(net);
 	if (sk)
 		rxe_sock_put(sk, rxe_ns_pernet_set_sk4, net);
@@ -662,6 +663,7 @@ void rxe_net_del(struct ib_device *dev)
 	sk = rxe_ns_pernet_sk6(net);
 	if (sk)
 		rxe_sock_put(sk, rxe_ns_pernet_set_sk6, net);
+	rxe_ns_pernet_sk_unlock(net);
 
 	dev_put(ndev);
 }
diff --git a/drivers/infiniband/sw/rxe/rxe_ns.c b/drivers/infiniband/sw/rxe/rxe_ns.c
index 8b9d734229b2..375c7d79d9d3 100644
--- a/drivers/infiniband/sw/rxe/rxe_ns.c
+++ b/drivers/infiniband/sw/rxe/rxe_ns.c
@@ -16,6 +16,7 @@
 struct rxe_ns_sock {
 	struct sock __rcu *rxe_sk4;
 	struct sock __rcu *rxe_sk6;
+	struct mutex rxe_sk_lock;
 };
 
 /*
@@ -28,9 +29,12 @@ static unsigned int rxe_pernet_id;
  */
 static int rxe_ns_init(struct net *net)
 {
+	struct rxe_ns_sock *ns_sk = net_generic(net, rxe_pernet_id);
+
 	/* defer socket create in the namespace to the first
 	 * device create.
 	 */
+	mutex_init(&ns_sk->rxe_sk_lock);
 
 	return 0;
 }
@@ -71,6 +75,20 @@ static struct pernet_operations rxe_net_ops = {
 	.size = sizeof(struct rxe_ns_sock),
 };
 
+void rxe_ns_pernet_sk_lock(struct net *net)
+{
+	struct rxe_ns_sock *ns_sk = net_generic(net, rxe_pernet_id);
+
+	mutex_lock(&ns_sk->rxe_sk_lock);
+}
+
+void rxe_ns_pernet_sk_unlock(struct net *net)
+{
+	struct rxe_ns_sock *ns_sk = net_generic(net, rxe_pernet_id);
+
+	mutex_unlock(&ns_sk->rxe_sk_lock);
+}
+
 struct sock *rxe_ns_pernet_sk4(struct net *net)
 {
 	struct rxe_ns_sock *ns_sk = net_generic(net, rxe_pernet_id);
diff --git a/drivers/infiniband/sw/rxe/rxe_ns.h b/drivers/infiniband/sw/rxe/rxe_ns.h
index 4da2709e6b71..c5262843bb63 100644
--- a/drivers/infiniband/sw/rxe/rxe_ns.h
+++ b/drivers/infiniband/sw/rxe/rxe_ns.h
@@ -3,6 +3,8 @@
 #ifndef RXE_NS_H
 #define RXE_NS_H
 
+void rxe_ns_pernet_sk_lock(struct net *net);
+void rxe_ns_pernet_sk_unlock(struct net *net);
 struct sock *rxe_ns_pernet_sk4(struct net *net);
 void rxe_ns_pernet_set_sk4(struct net *net, struct sock *sk);
 
-- 
2.54.0.rc2.544.gc7ae2d5bb8-goog