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kcm: switch order of device registration to fix a crash

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[ Upstream commit 3c446e6f96997f2a95bf0037ef463802162d2323 ]

When kcm is loaded while many processes try to create a KCM socket, a
crash occurs:
 BUG: unable to handle kernel NULL pointer dereference at 000000000000000e
 IP: mutex_lock+0x27/0x40 kernel/locking/mutex.c:240
 PGD 8000000016ef2067 P4D 8000000016ef2067 PUD 3d6e9067 PMD 0
 Oops: 0002 [#1] SMP KASAN PTI
 CPU: 0 PID: 7005 Comm: syz-executor.5 Not tainted 4.12.14-396-default #1 SLE15-SP1 (unreleased)
 RIP: 0010:mutex_lock+0x27/0x40 kernel/locking/mutex.c:240
 RSP: 0018:ffff88000d487a00 EFLAGS: 00010246
 RAX: 0000000000000000 RBX: 000000000000000e RCX: 1ffff100082b0719
 ...
 CR2: 000000000000000e CR3: 000000004b1bc003 CR4: 0000000000060ef0
 Call Trace:
  kcm_create+0x600/0xbf0 [kcm]
  __sock_create+0x324/0x750 net/socket.c:1272
 ...

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

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

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

Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby 2019-03-29 12:19:46 +01:00 committed by Greg Kroah-Hartman
parent b74c2990d0
commit 393c8b4c67
1 changed files with 8 additions and 8 deletions
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16
net/kcm/kcmsock.c
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@ -2059,14 +2059,14 @@ static int __init kcm_init(void)
if (err)
goto fail;
err = sock_register(&kcm_family_ops);
if (err)
goto sock_register_fail;
err = register_pernet_device(&kcm_net_ops);
if (err)
goto net_ops_fail;
err = sock_register(&kcm_family_ops);
if (err)
goto sock_register_fail;
err = kcm_proc_init();
if (err)
goto proc_init_fail;
@ -2074,12 +2074,12 @@ static int __init kcm_init(void)
return 0;
proc_init_fail:
unregister_pernet_device(&kcm_net_ops);
net_ops_fail:
sock_unregister(PF_KCM);
sock_register_fail:
unregister_pernet_device(&kcm_net_ops);
net_ops_fail:
proto_unregister(&kcm_proto);
fail:
@ -2095,8 +2095,8 @@ fail:
static void __exit kcm_exit(void)
{
kcm_proc_exit();
unregister_pernet_device(&kcm_net_ops);
sock_unregister(PF_KCM);
unregister_pernet_device(&kcm_net_ops);
proto_unregister(&kcm_proto);
destroy_workqueue(kcm_wq);