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authorJiri Slaby <jslaby@suse.cz>2019-03-29 14:19:46 +0300
committerDavid S. Miller <davem@davemloft.net>2019-04-02 00:59:20 +0300
commit3c446e6f96997f2a95bf0037ef463802162d2323 (patch)
tree97592244c45d13d7b2a4ea568e57b275b6d536c2 /net/kcm
parentc4df1bddc4306a08bc8ec6a65d34386388d2f42f (diff)
downloadlinux-3c446e6f96997f2a95bf0037ef463802162d2323.tar.xz
kcm: switch order of device registration to fix a crash
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>
Diffstat (limited to 'net/kcm')
-rw-r--r--net/kcm/kcmsock.c16
1 files changed, 8 insertions, 8 deletions
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index c5c5ab6c5a1c..44fdc641710d 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 @@ 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);