Messages in this thread | | | Date | Mon, 01 Apr 2019 14:59:55 -0700 (PDT) | Subject | Re: [PATCH] kcm: switch order of device registration to fix a crash | From | David Miller <> |
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From: Jiri Slaby <jslaby@suse.cz> Date: Fri, 29 Mar 2019 12:19:46 +0100
> 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>
Applied and queued up for -stable, thanks.
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