Jiri Slaby 3c446e6f96 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: ab7ac4eb98 ("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>		2019-04-01 14:59:20 -07:00
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kcmproc.c
kcmsock.c
Kconfig
Makefile