Once kobject_init_and_add() failed, pci_slot_release() is called to delete slot->list from parent->slots. But slot->list is intialized afterwards, so we ran into the following crash: Unable to handle kernel NULL pointer dereference at virtual address 00000000 ... CPU: 10 PID: 1 Comm: swapper/0 Not tainted 4.4.240 #197 task: ffffeb398a45ef10 task.stack: ffffeb398a470000 PC is at __list_del_entry_valid+0x5c/0xb0 LR is at pci_slot_release+0x84/0xe4 ... __list_del_entry_valid+0x5c/0xb0 pci_slot_release+0x84/0xe4 kobject_put+0x184/0x1c4 pci_create_slot+0x17c/0x1b4 __pci_hp_initialize+0x68/0xa4 pciehp_probe+0x1a4/0x2fc pcie_port_probe_service+0x58/0x84 driver_probe_device+0x320/0x470 __driver_attach+0x54/0xb8 bus_for_each_dev+0xc8/0xf0 driver_attach+0x30/0x3c bus_add_driver+0x1b0/0x24c driver_register+0x9c/0xe0 pcie_port_service_register+0x64/0x7c pcied_init+0x44/0xa4 do_one_initcall+0x1d0/0x1f0 kernel_init_freeable+0x24c/0x254 kernel_init+0x18/0xe8 ret_from_fork+0x10/0x20 Fixes: 8a94644b440e ("PCI: Fix pci_create_slot() reference count leak") Signed-off-by: Jubin Zhong <zhongjubin@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx #v4.4.235 ---- v2: Since both slot memory and slot->list would be handled by pci_slot_release(), we need to make sure slot->list is properly initialized beforehand. v1: https://lore.kernel.org/lkml/1606288971-47927-1-git-send-email-zhongjubin@xxxxxxxxxx/ Two things need to be cleaned up on pci_create_slot's error path: 1. free slot memory 2. remove slot->list from its parent->slots This patch mistakenly took slot memory as unfreed (which is not), and would introduce double free problem. --- drivers/pci/slot.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c index 3861505..ed2077e 100644 --- a/drivers/pci/slot.c +++ b/drivers/pci/slot.c @@ -272,6 +272,9 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr, goto err; } + INIT_LIST_HEAD(&slot->list); + list_add(&slot->list, &parent->slots); + err = kobject_init_and_add(&slot->kobj, &pci_slot_ktype, NULL, "%s", slot_name); if (err) { @@ -279,9 +282,6 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr, goto err; } - INIT_LIST_HEAD(&slot->list); - list_add(&slot->list, &parent->slots); - down_read(&pci_bus_sem); list_for_each_entry(dev, &parent->devices, bus_list) if (PCI_SLOT(dev->devfn) == slot_nr) -- 1.8.5.6