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Subject[PATCH 4.4 035/241] tipc: switch order of device registration to fix a crash
Date
From: Junwei Hu <hujunwei4@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 <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>
Signed-off-by: Greg Kroah-Hartman <gregkh@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");

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