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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-02-03 21:30:06 (GMT)
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-02-03 21:30:06 (GMT)
commit1b360f44d009059e446532f29c1a889951e72667 (patch)
treee30d762799671bda7d398fb8b6b0b0a31575d0cf /drivers/pci
parentd42f5da2340083301dd2c48ff2d75f6ce4b30767 (diff)
downloadlinux-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')
-rw-r--r--drivers/pci/hotplug/acpiphp_glue.c18
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;