[Devel] [PATCH RHEL7 COMMIT] net: fix false-positive deadlock detection for sk_receive_queue lock

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-957.12.2.vz7.96.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-957.12.2.vz7.96.1
------>
commit 6a1516602b04cbc461112b3a5dc8833e80449e94
Author: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Date:   Tue May 21 18:11:19 2019 +0300

    net: fix false-positive deadlock detection for sk_receive_queue lock
    
    Here is the code path of false-positive deadlock:
    
    CPU1                                    CPU2
    
    __udp_enqueue_schedule_skb
     spin_lock(sk->sk_receive_queue.lock) <- udp
    
                                            ipoib_start_xmit
                                             spin_lock_irqsave(((struct rdma_netdev *)netdev_priv(net_device))->clnt_priv->lock)
                                             path_rec_start
                                              ...
                                               __netlink_sendskb
                                                skb_queue_tail
                                                 spin_lock_irqsave(sk->sk_receive_queue.lock) <- netlink
    
    do_IRQ
     ...
      ipoib_cm_rx_event_handler
       spin_lock_irqsave(((struct rdma_netdev *)netdev_priv(net_device))->clnt_priv->lock)
    
    For sockets of different protocols these sk->sk_receive_queue.lock's
    are different on the right and on the left, thus no real deadlock will
    happen as CPU2 will continue execution instead of waiting for lock.
    
    So mark the udp lock with separate lockdep class.
    
    https://jira.sw.ru/browse/HCI-223
    https://pmc.acronis.com/browse/VSTOR-18951
    
    Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 include/linux/skbuff.h | 3 ++-
 include/net/sock.h     | 1 +
 net/core/sock.c        | 4 ++--
 net/ipv4/udp.c         | 3 +++
 4 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 28a112d06ece..a850fc9285fc 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1608,7 +1608,8 @@ static inline void skb_queue_head_init_class(struct sk_buff_head *list,
 		struct lock_class_key *class)
 {
 	skb_queue_head_init(list);
-	lockdep_set_class(&list->lock, class);
+	if (class)
+		lockdep_set_class(&list->lock, class);
 }
 
 /*
diff --git a/include/net/sock.h b/include/net/sock.h
index 6ac59b86b3a2..f90941ef02a2 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1083,6 +1083,7 @@ struct proto {
 	void			(*destroy_cgroup)(struct mem_cgroup *memcg);
 	struct cg_proto		*(*proto_cgroup)(struct mem_cgroup *memcg);
 #endif
+	struct lock_class_key	*lockdep_class;
 };
 
 /*
diff --git a/net/core/sock.c b/net/core/sock.c
index 97fdfa5da687..ffd747cc30a4 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1556,7 +1556,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
 		 */
 		atomic_set(&newsk->sk_wmem_alloc, 1);
 		atomic_set(&newsk->sk_omem_alloc, 0);
-		skb_queue_head_init(&newsk->sk_receive_queue);
+		skb_queue_head_init_class(&newsk->sk_receive_queue, newsk->sk_prot->lockdep_class);
 		skb_queue_head_init(&newsk->sk_write_queue);
 
 		rwlock_init(&newsk->sk_callback_lock);
@@ -2412,7 +2412,7 @@ EXPORT_SYMBOL(sk_stop_timer);
 
 void sock_init_data(struct socket *sock, struct sock *sk)
 {
-	skb_queue_head_init(&sk->sk_receive_queue);
+	skb_queue_head_init_class(&sk->sk_receive_queue, sk->sk_prot->lockdep_class);
 	skb_queue_head_init(&sk->sk_write_queue);
 	skb_queue_head_init(&sk->sk_error_queue);
 
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index a35aea149358..9c3efcb04a0c 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2315,6 +2315,8 @@ unsigned int udp_poll(struct file *file, struct socket *sock, poll_table *wait)
 }
 EXPORT_SYMBOL(udp_poll);
 
+static struct lock_class_key udp_sk_class;
+
 struct proto udp_prot = {
 	.name		   = "UDP",
 	.owner		   = THIS_MODULE,
@@ -2351,6 +2353,7 @@ struct proto udp_prot = {
 	.destroy_cgroup		= udp_destroy_cgroup,
 	.proto_cgroup		= udp_proto_cgroup,
 #endif
+	.lockdep_class		= udp_sk_class,
 };
 EXPORT_SYMBOL(udp_prot);