In the process of probing the driver 'cpcihp_zt5550', function 'pci_get_device' may fail, at this time 'cpci_hp_unregister_controller' will be called. Since the default value of 'thread_finished' is 0, 'cpci_stop_thread' will be executed, but at this time 'cpci_thread' has not been allocated, which leads to a null pointer dereference. Fix this by set 'thread_finished' to be true by default. This log reveals it: BUG: kernel NULL pointer dereference, address: 0000000000000028 PGD 0 P4D 0 Oops: 0002 [#1] PREEMPT SMP PTI CPU: 5 PID: 1 Comm: swapper/0 Not tainted 5.12.4-g70e7f0549188-dirty #74 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 RIP: 0010:kthread_stop+0x51/0x380 Code: b5 4e 10 00 65 8b 05 46 da e1 7e 89 c0 48 0f a3 05 5c c1 ef 05 0f 82 68 01 00 00 e8 99 4e 10 00 4c 8d 6b 28 41 bc 01 00 00 00 <f0> 44 0f c1 63 28 45 85 e4 0f 84 af 02 00 00 e8 7b 4e 10 00 45 85 RSP: 0000:ffffc90000017ba8 EFLAGS: 00010293 RAX: ffff888100850000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff811f3b37 RDI: ffffffff86259ca6 RBP: ffffc90000017bc8 R08: 0000000000000001 R09: 0000000000000001 R10: 0000000000000001 R11: 00000000ffffffff R12: 0000000000000001 R13: 0000000000000028 R14: ffff88810160a0c8 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88817b200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000028 CR3: 0000000006a32000 CR4: 00000000000006e0 Call Trace: cpci_stop_thread+0x1a/0x30 cpci_hp_unregister_controller+0x43/0xc0 zt5550_hc_init_one+0x67d/0x720 local_pci_probe+0x4f/0xb0 pci_device_probe+0x169/0x230 ? pci_device_remove+0x110/0x110 really_probe+0x283/0x650 driver_probe_device+0x89/0x1d0 ? mutex_lock_nested+0x1b/0x20 device_driver_attach+0x68/0x70 __driver_attach+0x11c/0x1b0 ? device_driver_attach+0x70/0x70 bus_for_each_dev+0xbb/0x110 ? rdinit_setup+0x45/0x45 driver_attach+0x27/0x30 bus_add_driver+0x1eb/0x2a0 driver_register+0xa9/0x180 __pci_register_driver+0x7c/0x90 ? cpci_hotplug_init+0x1c/0x1c zt5550_init+0x66/0x91 do_one_initcall+0x7f/0x3d0 ? rdinit_setup+0x45/0x45 ? rcu_read_lock_sched_held+0x4f/0x80 kernel_init_freeable+0x2d7/0x329 ? rest_init+0x2c0/0x2c0 kernel_init+0x18/0x190 ? rest_init+0x2c0/0x2c0 ? rest_init+0x2c0/0x2c0 ret_from_fork+0x1f/0x30 Modules linked in: Dumping ftrace buffer: (ftrace buffer empty) CR2: 0000000000000028 ---[ end trace ef108f49fd26a20c ]--- RIP: 0010:kthread_stop+0x51/0x380 Code: b5 4e 10 00 65 8b 05 46 da e1 7e 89 c0 48 0f a3 05 5c c1 ef 05 0f 82 68 01 00 00 e8 99 4e 10 00 4c 8d 6b 28 41 bc 01 00 00 00 <f0> 44 0f c1 63 28 45 85 e4 0f 84 af 02 00 00 e8 7b 4e 10 00 45 85 RSP: 0000:ffffc90000017ba8 EFLAGS: 00010293 RAX: ffff888100850000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff811f3b37 RDI: ffffffff86259ca6 RBP: ffffc90000017bc8 R08: 0000000000000001 R09: 0000000000000001 R10: 0000000000000001 R11: 00000000ffffffff R12: 0000000000000001 R13: 0000000000000028 R14: ffff88810160a0c8 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88817b200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000028 CR3: 0000000006a32000 CR4: 00000000000006e0 Kernel panic - not syncing: Fatal exception Dumping ftrace buffer: (ftrace buffer empty) Kernel Offset: disabled Rebooting in 1 seconds.. Signed-off-by: Zheyu Ma <zheyuma97@xxxxxxxxx> --- drivers/pci/hotplug/cpci_hotplug_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/pci/hotplug/cpci_hotplug_core.c b/drivers/pci/hotplug/cpci_hotplug_core.c index d0559d2faf50..d527aae4cc60 100644 --- a/drivers/pci/hotplug/cpci_hotplug_core.c +++ b/drivers/pci/hotplug/cpci_hotplug_core.c @@ -47,7 +47,7 @@ static atomic_t extracting; int cpci_debug; static struct cpci_hp_controller *controller; static struct task_struct *cpci_thread; -static int thread_finished; +static int thread_finished = 1; static int enable_slot(struct hotplug_slot *slot); static int disable_slot(struct hotplug_slot *slot); -- 2.17.6
