PCI: hotplug: Constify hotplug_slot_ops

Hotplug drivers cannot declare their hotplug_slot_ops const, making them
attractive targets for attackers, because upon registration of a hotplug
slot, __pci_hp_initialize() writes to the "owner" and "mod_name" members
in that struct.

Fix by moving these members to struct hotplug_slot and constify every
driver's hotplug_slot_ops except for pciehp.

pciehp constructs its hotplug_slot_ops at runtime based on the PCIe
port's capabilities, hence cannot declare them const.  It can be
converted to __write_rarely once that's mainlined:
http://www.openwall.com/lists/kernel-hardening/2016/11/16/3

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>  # drivers/pci/hotplug/rpa*
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com> # drivers/platform/x86
Cc: Len Brown <lenb@kernel.org>
Cc: Scott Murray <scott@spiteful.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Oliver OHalloran <oliveroh@au1.ibm.com>
Cc: Gavin Shan <gwshan@linux.vnet.ibm.com>
Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Corentin Chary <corentin.chary@gmail.com>
Cc: Darren Hart <dvhart@infradead.org>

1 files changed, 14 insertions, 13 deletions

diff --git a/drivers/pci/hotplug/pci_hotplug_core.c b/drivers/pci/hotplug/pci_hotplug_core.c
index 90fde5f106d8..ede2ed6f4ce0 100644
--- a/drivers/pci/hotplug/pci_hotplug_core.c
+++ b/drivers/pci/hotplug/pci_hotplug_core.c
@@ -49,15 +49,15 @@ static DEFINE_MUTEX(pci_hp_mutex);
 #define GET_STATUS(name, type)	\
 static int get_##name(struct hotplug_slot *slot, type *value)		\
 {									\
-	struct hotplug_slot_ops *ops = slot->ops;			\
+	const struct hotplug_slot_ops *ops = slot->ops;			\
 	int retval = 0;							\
-	if (!try_module_get(ops->owner))				\
+	if (!try_module_get(slot->owner))				\
 		return -ENODEV;						\
 	if (ops->get_##name)						\
 		retval = ops->get_##name(slot, value);			\
 	else								\
 		*value = slot->info->name;				\
-	module_put(ops->owner);						\
+	module_put(slot->owner);					\
 	return retval;							\
 }
 
@@ -90,7 +90,7 @@ static ssize_t power_write_file(struct pci_slot *pci_slot, const char *buf,
 	power = (u8)(lpower & 0xff);
 	dbg("power = %d\n", power);
 
-	if (!try_module_get(slot->ops->owner)) {
+	if (!try_module_get(slot->owner)) {
 		retval = -ENODEV;
 		goto exit;
 	}
@@ -109,7 +109,7 @@ static ssize_t power_write_file(struct pci_slot *pci_slot, const char *buf,
 		err("Illegal value specified for power\n");
 		retval = -EINVAL;
 	}
-	module_put(slot->ops->owner);
+	module_put(slot->owner);
 
 exit:
 	if (retval)
@@ -138,7 +138,8 @@ static ssize_t attention_read_file(struct pci_slot *pci_slot, char *buf)
 static ssize_t attention_write_file(struct pci_slot *pci_slot, const char *buf,
 				    size_t count)
 {
-	struct hotplug_slot_ops *ops = pci_slot->hotplug->ops;
+	struct hotplug_slot *slot = pci_slot->hotplug;
+	const struct hotplug_slot_ops *ops = slot->ops;
 	unsigned long lattention;
 	u8 attention;
 	int retval = 0;
@@ -147,13 +148,13 @@ static ssize_t attention_write_file(struct pci_slot *pci_slot, const char *buf,
 	attention = (u8)(lattention & 0xff);
 	dbg(" - attention = %d\n", attention);
 
-	if (!try_module_get(ops->owner)) {
+	if (!try_module_get(slot->owner)) {
 		retval = -ENODEV;
 		goto exit;
 	}
 	if (ops->set_attention_status)
-		retval = ops->set_attention_status(pci_slot->hotplug, attention);
-	module_put(ops->owner);
+		retval = ops->set_attention_status(slot, attention);
+	module_put(slot->owner);
 
 exit:
 	if (retval)
@@ -213,13 +214,13 @@ static ssize_t test_write_file(struct pci_slot *pci_slot, const char *buf,
 	test = (u32)(ltest & 0xffffffff);
 	dbg("test = %d\n", test);
 
-	if (!try_module_get(slot->ops->owner)) {
+	if (!try_module_get(slot->owner)) {
 		retval = -ENODEV;
 		goto exit;
 	}
 	if (slot->ops->hardware_test)
 		retval = slot->ops->hardware_test(slot, test);
-	module_put(slot->ops->owner);
+	module_put(slot->owner);
 
 exit:
 	if (retval)
@@ -447,8 +448,8 @@ int __pci_hp_initialize(struct hotplug_slot *slot, struct pci_bus *bus,
 	if ((slot->info == NULL) || (slot->ops == NULL))
 		return -EINVAL;
 
-	slot->ops->owner = owner;
-	slot->ops->mod_name = mod_name;
+	slot->owner = owner;
+	slot->mod_name = mod_name;
 
 	/*
 	 * No problems if we call this interface from both ACPI_PCI_SLOT