nvdimm_bus_register() could be called from other modules, such as nfit, but it can only be called after the nvdimm_bus_type is registered.
BUG: kernel NULL pointer dereference, address: 0000000000000098 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 117 Comm: systemd-udevd Not tainted 6.2.0-rc6-pmem+ #97 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 RIP: 0010:bus_add_device+0x58/0x150 Call Trace: <TASK> device_add+0x3ac/0x980 nvdimm_bus_register+0x16d/0x1d0 acpi_nfit_init+0xb72/0x1f90 [nfit] acpi_nfit_add+0x1d5/0x200 [nfit] acpi_device_probe+0x45/0x160 really_probe+0xce/0x390 __driver_probe_device+0x78/0x180 driver_probe_device+0x1e/0x90 __driver_attach+0xd6/0x1d0 bus_for_each_dev+0x7b/0xc0 bus_add_driver+0x1ac/0x200 driver_register+0x8f/0xf0 nfit_init+0x164/0xff0 [nfit] do_one_initcall+0x5b/0x320 do_init_module+0x4c/0x1f0 __do_sys_finit_module+0xb4/0x130 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc Signed-off-by: Li Zhijian <lizhij...@fujitsu.com> --- drivers/nvdimm/bus.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c index ada61bbf49c1..ea66053072cb 100644 --- a/drivers/nvdimm/bus.c +++ b/drivers/nvdimm/bus.c @@ -28,6 +28,7 @@ static int nvdimm_bus_major; struct class *nd_class; static DEFINE_IDA(nd_ida); +static bool nvdimm_bus_type_registered; static int to_nd_device_type(struct device *dev) { @@ -337,6 +338,10 @@ struct nvdimm_bus *nvdimm_bus_register(struct device *parent, struct nvdimm_bus *nvdimm_bus; int rc; + if (!nvdimm_bus_type_registered) { + pr_warn("nvdimm bus type is not registered\n"); + return NULL; + } nvdimm_bus = kzalloc(sizeof(*nvdimm_bus), GFP_KERNEL); if (!nvdimm_bus) return NULL; @@ -1321,6 +1326,7 @@ int __init nvdimm_bus_init(void) if (rc) goto err_nd_bus; + nvdimm_bus_type_registered = true; return 0; err_nd_bus: @@ -1343,4 +1349,5 @@ void nvdimm_bus_exit(void) unregister_chrdev(nvdimm_major, "dimmctl"); bus_unregister(&nvdimm_bus_type); ida_destroy(&nd_ida); + nvdimm_bus_type_registered = false; } -- 1.8.3.1