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>

drivers/pci/hotplug/acpiphp_core.c

@@ -57,7 +57,7 @@ static int get_attention_status(struct hotplug_slot *slot, u8 *value);
 static int get_latch_status(struct hotplug_slot *slot, u8 *value);
 static int get_adapter_status(struct hotplug_slot *slot, u8 *value);
 
-static struct hotplug_slot_ops acpi_hotplug_slot_ops = {
+static const struct hotplug_slot_ops acpi_hotplug_slot_ops = {
 	.enable_slot		= enable_slot,
 	.disable_slot		= disable_slot,
 	.set_attention_status	= set_attention_status,

drivers/pci/hotplug/cpci_hotplug_core.c

@@ -57,7 +57,7 @@ static int get_attention_status(struct hotplug_slot *slot, u8 *value);
 static int get_adapter_status(struct hotplug_slot *slot, u8 *value);
 static int get_latch_status(struct hotplug_slot *slot, u8 *value);
 
-static struct hotplug_slot_ops cpci_hotplug_slot_ops = {
+static const struct hotplug_slot_ops cpci_hotplug_slot_ops = {
 	.enable_slot = enable_slot,
 	.disable_slot = disable_slot,
 	.set_attention_status = set_attention_status,

drivers/pci/hotplug/cpqphp_core.c

@@ -560,7 +560,7 @@ static int get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value)
 	return 0;
 }
 
-static struct hotplug_slot_ops cpqphp_hotplug_slot_ops = {
+static const struct hotplug_slot_ops cpqphp_hotplug_slot_ops = {
 	.set_attention_status =	set_attention_status,
 	.enable_slot =		process_SI,
 	.disable_slot =		process_SS,

drivers/pci/hotplug/ibmphp.h

@@ -740,7 +740,7 @@ int ibmphp_do_disable_slot(struct slot *slot_cur);
 int ibmphp_update_slot_info(struct slot *);	/* This function is called from HPC, so we need it to not be be static */
 int ibmphp_configure_card(struct pci_func *, u8);
 int ibmphp_unconfigure_card(struct slot **, int);
-extern struct hotplug_slot_ops ibmphp_hotplug_slot_ops;
+extern const struct hotplug_slot_ops ibmphp_hotplug_slot_ops;
 
 #endif				//__IBMPHP_H
 

drivers/pci/hotplug/ibmphp_core.c

@@ -1259,7 +1259,7 @@ error:
 	goto exit;
 }
 
-struct hotplug_slot_ops ibmphp_hotplug_slot_ops = {
+const struct hotplug_slot_ops ibmphp_hotplug_slot_ops = {
 	.set_attention_status =		set_attention_status,
 	.enable_slot =			enable_slot,
 	.disable_slot =			ibmphp_disable_slot,

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

drivers/pci/hotplug/pnv_php.c

@@ -530,7 +530,7 @@ static int pnv_php_disable_slot(struct hotplug_slot *slot)
 	return ret;
 }
 
-static struct hotplug_slot_ops php_slot_ops = {
+static const struct hotplug_slot_ops php_slot_ops = {
 	.get_power_status	= pnv_php_get_power_state,
 	.get_adapter_status	= pnv_php_get_adapter_state,
 	.set_attention_status	= pnv_php_set_attention_state,

drivers/pci/hotplug/rpaphp.h

@@ -70,7 +70,7 @@ struct slot {
 	struct hotplug_slot *hotplug_slot;
 };
 
-extern struct hotplug_slot_ops rpaphp_hotplug_slot_ops;
+extern const struct hotplug_slot_ops rpaphp_hotplug_slot_ops;
 extern struct list_head rpaphp_slot_head;
 
 /* function prototypes */

drivers/pci/hotplug/rpaphp_core.c

@@ -477,7 +477,7 @@ static int disable_slot(struct hotplug_slot *hotplug_slot)
 	return 0;
 }
 
-struct hotplug_slot_ops rpaphp_hotplug_slot_ops = {
+const struct hotplug_slot_ops rpaphp_hotplug_slot_ops = {
 	.enable_slot = enable_slot,
 	.disable_slot = disable_slot,
 	.set_attention_status = set_attention_status,

drivers/pci/hotplug/s390_pci_hpc.c

@@ -130,7 +130,7 @@ static int get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value)
 	return 0;
 }
 
-static struct hotplug_slot_ops s390_hotplug_slot_ops = {
+static const struct hotplug_slot_ops s390_hotplug_slot_ops = {
 	.enable_slot =		enable_slot,
 	.disable_slot =		disable_slot,
 	.get_power_status =	get_power_status,

drivers/pci/hotplug/sgi_hotplug.c

@@ -80,7 +80,7 @@ static int enable_slot(struct hotplug_slot *slot);
 static int disable_slot(struct hotplug_slot *slot);
 static inline int get_power_status(struct hotplug_slot *slot, u8 *value);
 
-static struct hotplug_slot_ops sn_hotplug_slot_ops = {
+static const struct hotplug_slot_ops sn_hotplug_slot_ops = {
 	.enable_slot            = enable_slot,
 	.disable_slot           = disable_slot,
 	.get_power_status       = get_power_status,

drivers/pci/hotplug/shpchp_core.c

@@ -51,7 +51,7 @@ static int get_attention_status(struct hotplug_slot *slot, u8 *value);
 static int get_latch_status(struct hotplug_slot *slot, u8 *value);
 static int get_adapter_status(struct hotplug_slot *slot, u8 *value);
 
-static struct hotplug_slot_ops shpchp_hotplug_slot_ops = {
+static const struct hotplug_slot_ops shpchp_hotplug_slot_ops = {
 	.set_attention_status =	set_attention_status,
 	.enable_slot =		enable_slot,
 	.disable_slot =		disable_slot,

drivers/pci/pci.c

@@ -4571,13 +4571,13 @@ static int pci_reset_hotplug_slot(struct hotplug_slot *hotplug, int probe)
 {
 	int rc = -ENOTTY;
 
-	if (!hotplug || !try_module_get(hotplug->ops->owner))
+	if (!hotplug || !try_module_get(hotplug->owner))
 		return rc;
 
 	if (hotplug->ops->reset_slot)
 		rc = hotplug->ops->reset_slot(hotplug, probe);
 
-	module_put(hotplug->ops->owner);
+	module_put(hotplug->owner);
 
 	return rc;
 }

drivers/pci/slot.c

@@ -371,7 +371,7 @@ void pci_hp_create_module_link(struct pci_slot *pci_slot)
 
 	if (!slot || !slot->ops)
 		return;
-	kobj = kset_find_obj(module_kset, slot->ops->mod_name);
+	kobj = kset_find_obj(module_kset, slot->mod_name);
 	if (!kobj)
 		return;
 	ret = sysfs_create_link(&pci_slot->kobj, kobj, "module");

drivers/platform/x86/asus-wmi.c

@@ -868,8 +868,7 @@ static int asus_get_adapter_status(struct hotplug_slot *hotplug_slot,
 	return 0;
 }
 
-static struct hotplug_slot_ops asus_hotplug_slot_ops = {
-	.owner = THIS_MODULE,
+static const struct hotplug_slot_ops asus_hotplug_slot_ops = {
 	.get_adapter_status = asus_get_adapter_status,
 	.get_power_status = asus_get_adapter_status,
 };

drivers/platform/x86/eeepc-laptop.c

@@ -726,8 +726,7 @@ static int eeepc_get_adapter_status(struct hotplug_slot *hotplug_slot,
 	return 0;
 }
 
-static struct hotplug_slot_ops eeepc_hotplug_slot_ops = {
-	.owner = THIS_MODULE,
+static const struct hotplug_slot_ops eeepc_hotplug_slot_ops = {
 	.get_adapter_status = eeepc_get_adapter_status,
 	.get_power_status = eeepc_get_adapter_status,
 };

include/linux/pci_hotplug.h

@@ -16,8 +16,6 @@
 
 /**
  * struct hotplug_slot_ops -the callbacks that the hotplug pci core can use
- * @owner: The module owner of this structure
- * @mod_name: The module name (KBUILD_MODNAME) of this structure
  * @enable_slot: Called when the user wants to enable a specific pci slot
  * @disable_slot: Called when the user wants to disable a specific pci slot
  * @set_attention_status: Called to set the specific slot's attention LED to
@@ -46,8 +44,6 @@
  * set an LED, enable / disable power, etc.)
  */
 struct hotplug_slot_ops {
-	struct module *owner;
-	const char *mod_name;
 	int (*enable_slot)		(struct hotplug_slot *slot);
 	int (*disable_slot)		(struct hotplug_slot *slot);
 	int (*set_attention_status)	(struct hotplug_slot *slot, u8 value);
@@ -82,15 +78,19 @@ struct hotplug_slot_info {
  * this slot.
  * @private: used by the hotplug pci controller driver to store whatever it
  * needs.
+ * @owner: The module owner of this structure
+ * @mod_name: The module name (KBUILD_MODNAME) of this structure
  */
 struct hotplug_slot {
-	struct hotplug_slot_ops		*ops;
+	const struct hotplug_slot_ops	*ops;
 	struct hotplug_slot_info	*info;
 	void				*private;
 
 	/* Variables below this are for use only by the hotplug pci core. */
 	struct list_head		slot_list;
 	struct pci_slot			*pci_slot;
+	struct module			*owner;
+	const char			*mod_name;
 };
 
 static inline const char *hotplug_slot_name(const struct hotplug_slot *slot)