| From 47ea0519a55b1bb556e972fb58161439e6ad39c6 Mon Sep 17 00:00:00 2001 |
| From: Jiri Slaby <jslaby@suse.cz> |
| Date: Fri, 29 Mar 2019 12:19:46 +0100 |
| Subject: kcm: switch order of device registration to fix a crash |
| |
| [ 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: Sasha Levin <sashal@kernel.org> |
| --- |
| net/kcm/kcmsock.c | 16 ++++++++-------- |
| 1 file changed, 8 insertions(+), 8 deletions(-) |
| |
| diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c |
| index 571d824e4e24..b919db02c7f9 100644 |
| --- a/net/kcm/kcmsock.c |
| +++ b/net/kcm/kcmsock.c |
| @@ -2054,14 +2054,14 @@ 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; |
| @@ -2069,12 +2069,12 @@ 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: |
| @@ -2090,8 +2090,8 @@ static int __init kcm_init(void) |
| 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); |
| |
| -- |
| 2.19.1 |
| |