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author | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2014-02-03 21:30:06 (GMT) |
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committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2014-02-03 21:30:06 (GMT) |
commit | 1b360f44d009059e446532f29c1a889951e72667 (patch) | |
tree | e30d762799671bda7d398fb8b6b0b0a31575d0cf /drivers/pci/hotplug | |
parent | d42f5da2340083301dd2c48ff2d75f6ce4b30767 (diff) | |
download | linux-1b360f44d009059e446532f29c1a889951e72667.tar.xz |
ACPI / hotplug / PCI: Fix bridge removal race in handle_hotplug_event()
If a PCI bridge with an ACPIPHP context attached is removed via
sysfs, the code path executed as a result is the following:
pci_stop_and_remove_bus_device_locked
pci_remove_bus
pcibios_remove_bus
acpi_pci_remove_bus
acpiphp_remove_slots
cleanup_bridge
put_bridge
free_bridge
acpiphp_put_context (for each child, under context lock)
kfree (child context)
Now, if a hotplug notify is dispatched for one of the bridge's
children and the timing is such that handle_hotplug_event() for
that notify is executed while free_bridge() above is running,
the get_bridge(context->func.parent) in handle_hotplug_event()
will not really help, because it is too late to prevent the bridge
from going away and the child's context may be freed before
hotplug_event_work() scheduled from handle_hotplug_event()
dereferences the pointer to it passed via the data argument.
That will cause a kernel crash to happpen in hotplug_event_work().
To prevent that from happening, make handle_hotplug_event()
check the is_going_away flag of the function's parent bridge
(under acpiphp_context_lock) and bail out if it's set. Also,
make cleanup_bridge() set the bridge's is_going_away flag under
acpiphp_context_lock so that it cannot be changed between the
check and the subsequent get_bridge(context->func.parent) in
handle_hotplug_event().
Then, in the above scenario, handle_hotplug_event() will notice
that context->func.parent->is_going_away is already set and it
will exit immediately preventing the crash from happening.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/pci/hotplug')
-rw-r--r-- | drivers/pci/hotplug/acpiphp_glue.c | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c index 931d0b4..91eceaf 100644 --- a/drivers/pci/hotplug/acpiphp_glue.c +++ b/drivers/pci/hotplug/acpiphp_glue.c @@ -441,7 +441,9 @@ static void cleanup_bridge(struct acpiphp_bridge *bridge) list_del(&bridge->list); mutex_unlock(&bridge_mutex); + mutex_lock(&acpiphp_context_lock); bridge->is_going_away = true; + mutex_unlock(&acpiphp_context_lock); } /** @@ -941,6 +943,7 @@ static void handle_hotplug_event(acpi_handle handle, u32 type, void *data) { struct acpiphp_context *context; u32 ost_code = ACPI_OST_SC_SUCCESS; + acpi_status status; switch (type) { case ACPI_NOTIFY_BUS_CHECK: @@ -976,13 +979,20 @@ static void handle_hotplug_event(acpi_handle handle, u32 type, void *data) mutex_lock(&acpiphp_context_lock); context = acpiphp_get_context(handle); - if (context && !WARN_ON(context->handle != handle)) { - get_bridge(context->func.parent); - acpiphp_put_context(context); - acpi_hotplug_execute(hotplug_event_work, context, type); + if (!context || WARN_ON(context->handle != handle) + || context->func.parent->is_going_away) + goto err_out; + + get_bridge(context->func.parent); + acpiphp_put_context(context); + status = acpi_hotplug_execute(hotplug_event_work, context, type); + if (ACPI_SUCCESS(status)) { mutex_unlock(&acpiphp_context_lock); return; } + put_bridge(context->func.parent); + + err_out: mutex_unlock(&acpiphp_context_lock); ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; |