tipc: wait and exit until all work queues are done

commit 04c26faa51d1e2fe71cf13c45791f5174c37f986 upstream.

On some host, a crash could be triggered simply by repeating these
commands several times:

  # modprobe tipc
  # tipc bearer enable media udp name UDP1 localip 127.0.0.1
  # rmmod tipc

  [] BUG: unable to handle kernel paging request at ffffffffc096bb00
  [] Workqueue: events 0xffffffffc096bb00
  [] Call Trace:
  []  ? process_one_work+0x1a7/0x360
  []  ? worker_thread+0x30/0x390
  []  ? create_worker+0x1a0/0x1a0
  []  ? kthread+0x116/0x130
  []  ? kthread_flush_work_fn+0x10/0x10
  []  ? ret_from_fork+0x35/0x40

When removing the TIPC module, the UDP tunnel sock will be delayed to
release in a work queue as sock_release() can't be done in rtnl_lock().
If the work queue is schedule to run after the TIPC module is removed,
kernel will crash as the work queue function cleanup_beareri() code no
longer exists when trying to invoke it.

To fix it, this patch introduce a member wq_count in tipc_net to track
the numbers of work queues in schedule, and  wait and exit until all
work queues are done in tipc_exit_net().

Fixes: d0f91938bede ("tipc: add ip/udp media type")
Reported-by: Shuang Li <shuali@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/tipc/core.c b/net/tipc/core.c
index c2ff429..40c0308 100644 (file)
--- a/net/tipc/core.c
+++ b/net/tipc/core.c
@@ -121,6 +121,8 @@ static void __net_exit tipc_exit_net(struct net *net)
 #ifdef CONFIG_TIPC_CRYPTO
        tipc_crypto_stop(&tipc_net(net)->crypto_tx);
 #endif
+       while (atomic_read(&tn->wq_count))
+               cond_resched();
 }
 
 static void __net_exit tipc_pernet_pre_exit(struct net *net)

diff --git a/net/tipc/core.h b/net/tipc/core.h
index 1d57a4d..992924a 100644 (file)
--- a/net/tipc/core.h
+++ b/net/tipc/core.h
@@ -151,6 +151,8 @@ struct tipc_net {
 #endif
        /* Work item for net finalize */
        struct tipc_net_work final_work;
+       /* The numbers of work queues in schedule */
+       atomic_t wq_count;
 };
 
 static inline struct tipc_net *tipc_net(struct net *net)

diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
index 1d17f44..a236281 100644 (file)
--- a/net/tipc/udp_media.c
+++ b/net/tipc/udp_media.c
@@ -806,6 +806,7 @@ static void cleanup_bearer(struct work_struct *work)
                kfree_rcu(rcast, rcu);
        }
 
+       atomic_dec(&tipc_net(sock_net(ub->ubsock->sk))->wq_count);
        dst_cache_destroy(&ub->rcast.dst_cache);
        udp_tunnel_sock_release(ub->ubsock);
        synchronize_net();
@@ -826,6 +827,7 @@ static void tipc_udp_disable(struct tipc_bearer *b)
        RCU_INIT_POINTER(ub->bearer, NULL);
 
        /* sock_release need to be done outside of rtnl lock */
+       atomic_inc(&tipc_net(sock_net(ub->ubsock->sk))->wq_count);
        INIT_WORK(&ub->work, cleanup_bearer);
        schedule_work(&ub->work);
 }