[PATCH 4.4 035/241] tipc: switch order of device registration to fix a crash

[Greg Kroah-Hartman]

From: Junwei Hu <hujunw...@huawei.com>

[ Upstream commit 7e27e8d6130c5e88fac9ddec4249f7f2337fe7f8 ]

When tipc is loaded while many processes try to create a TIPC socket,
a crash occurs:
 PANIC: Unable to handle kernel paging request at virtual
 address "dfff20000000021d"
 pc : tipc_sk_create+0x374/0x1180 [tipc]
 lr : tipc_sk_create+0x374/0x1180 [tipc]
   Exception class = DABT (current EL), IL = 32 bits
 Call trace:
  tipc_sk_create+0x374/0x1180 [tipc]
  __sock_create+0x1cc/0x408
  __sys_socket+0xec/0x1f0
  __arm64_sys_socket+0x74/0xa8
 ...

This is due to race between sock_create and unfinished
register_pernet_device. tipc_sk_insert tries to do
"net_generic(net, tipc_net_id)".
but tipc_net_id is not initialized yet.

So switch the order of the two to close the race.

This can be reproduced with multiple processes doing socket(AF_TIPC, ...)
and one process doing module removal.

Fixes: a62fbccecd62 ("tipc: make subscriber server support net namespace")
Signed-off-by: Junwei Hu <hujunw...@huawei.com>
Reported-by: Wang Wang <wangwa...@huawei.com>
Reviewed-by: Xiaogang Wang <wangxiaoga...@huawei.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/tipc/core.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/net/tipc/core.c
+++ b/net/tipc/core.c
@@ -126,10 +126,6 @@ static int __init tipc_init(void)
        if (err)
                goto out_netlink_compat;
 
-       err = tipc_socket_init();
-       if (err)
-               goto out_socket;
-
        err = tipc_register_sysctl();
        if (err)
                goto out_sysctl;
@@ -138,6 +134,10 @@ static int __init tipc_init(void)
        if (err)
                goto out_pernet;
 
+       err = tipc_socket_init();
+       if (err)
+               goto out_socket;
+
        err = tipc_bearer_setup();
        if (err)
                goto out_bearer;
@@ -145,12 +145,12 @@ static int __init tipc_init(void)
        pr_info("Started in single node mode\n");
        return 0;
 out_bearer:
+       tipc_socket_stop();
+out_socket:
        unregister_pernet_subsys(&tipc_net_ops);
 out_pernet:
        tipc_unregister_sysctl();
 out_sysctl:
-       tipc_socket_stop();
-out_socket:
        tipc_netlink_compat_stop();
 out_netlink_compat:
        tipc_netlink_stop();
@@ -162,10 +162,10 @@ out_netlink:
 static void __exit tipc_exit(void)
 {
        tipc_bearer_cleanup();
+       tipc_socket_stop();
        unregister_pernet_subsys(&tipc_net_ops);
        tipc_netlink_stop();
        tipc_netlink_compat_stop();
-       tipc_socket_stop();
        tipc_unregister_sysctl();
 
        pr_info("Deactivated\n");