From: Jiri Slaby jslaby@suse.cz
[ 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 --- net/kcm/kcmsock.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
--- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -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);