Commit 7e27e8d6 authored May 16, 2019 by Junwei Hu Committed by David S. Miller May 16, 2019

tipc: switch order of device registration to fix a crash



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: a62fbcce ("tipc: make subscriber server support net namespace")
Signed-off-by: Junwei Hu <hujunwei4@huawei.com>
Reported-by: Wang Wang <wangwang2@huawei.com>
Reviewed-by: Xiaogang Wang <wangxiaogang3@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 61fb0d01

net/tipc/core.c

+7 −7

Original line number	Diff line number	Diff line
		@@ -131,10 +131,6 @@ 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;
		@@ -143,6 +139,10 @@ 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;
		@@ -150,12 +150,12 @@ 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();
		@@ -167,10 +167,10 @@ 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");

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