[PATCH] PCI Hotplug: acpiphp: don't store a pci_dev in acpiphp_func

From: Alex Chiang
Date: Thu May 21 2009 - 18:21:28 EST

An oops can occur if a user attempts to use both PCI logical
hotplug and the ACPI physical hotplug driver (acpiphp) in this
sequence, where $slot/address == $device.

In other words, if acpiphp has claimed a PCI device, and that
device is logically removed, then acpiphp may oops when it
attempts to access it again.

# echo 1 > /sys/bus/pci/devices/$device/remove
# echo 0 > /sys/bus/pci/slots/$slot/power

Unable to handle kernel NULL pointer dereference (address 0000000000000000)
Call Trace:
[<a000000100016390>] show_stack+0x50/0xa0
[<a000000100016c60>] show_regs+0x820/0x860
[<a00000010003b390>] die+0x190/0x2a0
[<a000000100066a40>] ia64_do_page_fault+0x8e0/0xa40
[<a00000010000c7a0>] ia64_native_leave_kernel+0x0/0x270
[<a0000001003b2660>] pci_remove_bus_device+0x120/0x260
[<a0000002060549f0>] acpiphp_disable_slot+0x410/0x540 [acpiphp]
[<a0000002060505c0>] disable_slot+0xc0/0x120 [acpiphp]
[<a0000002040d21c0>] power_write_file+0x1e0/0x2a0 [pci_hotplug]
[<a0000001003bb820>] pci_slot_attr_store+0x60/0xa0
[<a000000100240f70>] sysfs_write_file+0x230/0x2c0
[<a000000100195750>] vfs_write+0x190/0x2e0
[<a0000001001961a0>] sys_write+0x80/0x100
[<a00000010000c600>] ia64_ret_from_syscall+0x0/0x20
[<a000000000010720>] __kernel_syscall_via_break+0x0/0x20

The root cause of this oops is that the logical remove ("echo 1 >
/sys/bus/pci/devices/$device/remove") destroyed the pci_dev. The
pci_dev struct itself wasn't deallocated because acpiphp kept a
reference, but some of its fields became invalid.

acpiphp doesn't have any real reason to keep a pointer to a
pci_dev around. It can always derive it using pci_get_slot().

If a logical remove destroys the pci_dev, acpiphp won't find it
and is thus prevented from causing mischief.

Reported-by: Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx>
Acked-by: Bjorn Helgaas <bjorn.helgaas@xxxxxx>
Signed-off-by: Alex Chiang <achiang@xxxxxx>
---
acpiphp.h | 1
acpiphp_glue.c | 63
+++++++++++++++++++++++----------------------------------
2 files changed, 26 insertions(+), 38 deletions(-)
---
diff --git a/drivers/pci/hotplug/acpiphp.h b/drivers/pci/hotplug/acpiphp.h
index 4fc168b..e68d5f2 100644
--- a/drivers/pci/hotplug/acpiphp.h
+++ b/drivers/pci/hotplug/acpiphp.h
@@ -129,7 +129,6 @@ struct acpiphp_func {
struct acpiphp_bridge *bridge; /* Ejectable PCI-to-PCI bridge */

struct list_head sibling;
- struct pci_dev *pci_dev;
struct notifier_block nb;
acpi_handle handle;

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index a33794d..3a6064b 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -32,9 +32,6 @@

/*
* Lifetime rules for pci_dev:
- * - The one in acpiphp_func has its refcount elevated by pci_get_slot()
- * when the driver is loaded or when an insertion event occurs. It loses
- * a refcount when its ejected or the driver unloads.
* - The one in acpiphp_bridge has its refcount elevated by pci_get_slot()
* when the bridge is scanned and it loses a refcount when the bridge
* is removed.
@@ -130,6 +127,7 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
unsigned long long adr, sun;
int device, function, retval;
struct pci_bus *pbus = bridge->pci_bus;
+ struct pci_dev *pdev;

if (!acpi_pci_check_ejectable(pbus, handle) && !is_dock_device(handle))
return AE_OK;
@@ -213,10 +211,10 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
newfunc->slot = slot;
list_add_tail(&newfunc->sibling, &slot->funcs);

- /* associate corresponding pci_dev */
- newfunc->pci_dev = pci_get_slot(pbus, PCI_DEVFN(device, function));
- if (newfunc->pci_dev) {
+ pdev = pci_get_slot(pbus, PCI_DEVFN(device, function));
+ if (pdev) {
slot->flags |= (SLOT_ENABLED | SLOT_POWEREDON);
+ pci_dev_put(pdev);
}

if (is_dock_device(handle)) {
@@ -617,7 +615,6 @@ static void cleanup_bridge(struct acpiphp_bridge *bridge)
if (ACPI_FAILURE(status))
err("failed to remove notify handler\n");
}
- pci_dev_put(func->pci_dev);
list_del(list);
kfree(func);
}
@@ -1101,22 +1098,24 @@ static int __ref enable_device(struct acpiphp_slot *slot)
pci_enable_bridges(bus);
pci_bus_add_devices(bus);

- /* associate pci_dev to our representation */
list_for_each (l, &slot->funcs) {
func = list_entry(l, struct acpiphp_func, sibling);
- func->pci_dev = pci_get_slot(bus, PCI_DEVFN(slot->device,
- func->function));
- if (!func->pci_dev)
+ dev = pci_get_slot(bus, PCI_DEVFN(slot->device,
+ func->function));
+ if (!dev)
continue;

- if (func->pci_dev->hdr_type != PCI_HEADER_TYPE_BRIDGE &&
- func->pci_dev->hdr_type != PCI_HEADER_TYPE_CARDBUS)
+ if (dev->hdr_type != PCI_HEADER_TYPE_BRIDGE &&
+ dev->hdr_type != PCI_HEADER_TYPE_CARDBUS) {
+ pci_dev_put(dev);
continue;
+ }

status = find_p2p_bridge(func->handle, (u32)1, bus, NULL);
if (ACPI_FAILURE(status))
warn("find_p2p_bridge failed (error code = 0x%x)\n",
status);
+ pci_dev_put(dev);
}

slot->flags |= SLOT_ENABLED;
@@ -1142,17 +1141,14 @@ static void disable_bridges(struct pci_bus *bus)
*/
static int disable_device(struct acpiphp_slot *slot)
{
- int retval = 0;
struct acpiphp_func *func;
- struct list_head *l;
+ struct pci_dev *pdev;

/* is this slot already disabled? */
if (!(slot->flags & SLOT_ENABLED))
goto err_exit;

- list_for_each (l, &slot->funcs) {
- func = list_entry(l, struct acpiphp_func, sibling);
-
+ list_for_each_entry(func, &slot->funcs, sibling) {
if (func->bridge) {
/* cleanup p2p bridges under this P2P bridge */
cleanup_p2p_bridge(func->bridge->handle,
@@ -1160,35 +1156,28 @@ static int disable_device(struct acpiphp_slot *slot)
func->bridge = NULL;
}

- if (func->pci_dev) {
- pci_stop_bus_device(func->pci_dev);
- if (func->pci_dev->subordinate) {
- disable_bridges(func->pci_dev->subordinate);
- pci_disable_device(func->pci_dev);
+ pdev = pci_get_slot(slot->bridge->pci_bus,
+ PCI_DEVFN(slot->device, func->function));
+ if (pdev) {
+ pci_stop_bus_device(pdev);
+ if (pdev->subordinate) {
+ disable_bridges(pdev->subordinate);
+ pci_disable_device(pdev);
}
+ pci_remove_bus_device(pdev);
+ pci_dev_put(pdev);
}
}

- list_for_each (l, &slot->funcs) {
- func = list_entry(l, struct acpiphp_func, sibling);
-
+ list_for_each_entry(func, &slot->funcs, sibling) {
acpiphp_unconfigure_ioapics(func->handle);
acpiphp_bus_trim(func->handle);
- /* try to remove anyway.
- * acpiphp_bus_add might have been failed */
-
- if (!func->pci_dev)
- continue;
-
- pci_remove_bus_device(func->pci_dev);
- pci_dev_put(func->pci_dev);
- func->pci_dev = NULL;
}

slot->flags &= (~SLOT_ENABLED);

- err_exit:
- return retval;
+err_exit:
+ return 0;
}



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