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Date: Wed, 27 May 2009 02:05:38 -0700
From: Jesse Barnes <jbarnes@...tuousgeek.org>
To: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
Cc: Alex Chiang <achiang@...com>, bjorn.helgaas@...com,
linux-pci <linux-pci@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI Hotplug: acpiphp: don't store a pci_dev in
acpiphp_func
On Tue, 26 May 2009 08:55:22 +0900
Kenji Kaneshige <kaneshige.kenji@...fujitsu.com> wrote:
> Alex Chiang wrote:
> > 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@...fujitsu.com>
> > Acked-by: Bjorn Helgaas <bjorn.helgaas@...com>
> > Signed-off-by: Alex Chiang <achiang@...com>
> > ---
> > 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;
> > }
> >
>
> The patch looks good to me. I confirmed it fixes the kernel oops
> problem on my test environment.
>
> Reviewed-by: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
> Tested-by: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
Thanks guys, I just pushed this to my for-linus tree. Assuming Linus
hasn't released yet, I'll send this over to him tomorrow.
Thanks,
Jesse
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