kernfs: pass struct ns_common instead of const void * for namespace tags

kernfs has historically used const void * to pass around namespace tags
used for directory-level namespace filtering. The only current user of
this is sysfs network namespace tagging where struct net pointers are
cast to void *.

Replace all const void * namespace parameters with const struct
ns_common * throughout the kernfs, sysfs, and kobject namespace layers.
This includes the kobj_ns_type_operations callbacks, kobject_namespace(),
and all sysfs/kernfs APIs that accept or return namespace tags.

Passing struct ns_common is needed because various codepaths require
access to the underlying namespace. A struct ns_common can always be
converted back to the concrete namespace type (e.g., struct net) via
container_of() or to_ns_common() in the reverse direction.

This is a preparatory change for switching to ns_id-based directory
iteration to prevent a KASLR pointer leak through the current use of
raw namespace pointers as hash seeds and comparison keys.

Signed-off-by: Christian Brauner <brauner@kernel.org>

7 files changed, 20 insertions, 17 deletions

diff --git a/drivers/base/class.c b/drivers/base/class.c
index 827fc7adacc7..ffab0a9c8ccb 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -127,7 +127,7 @@ static const struct kobj_type class_ktype = {
 };
 
 int class_create_file_ns(const struct class *cls, const struct class_attribute *attr,
-			 const void *ns)
+			 const struct ns_common *ns)
 {
 	struct subsys_private *sp = class_to_subsys(cls);
 	int error;
@@ -143,7 +143,7 @@ int class_create_file_ns(const struct class *cls, const struct class_attribute *
 EXPORT_SYMBOL_GPL(class_create_file_ns);
 
 void class_remove_file_ns(const struct class *cls, const struct class_attribute *attr,
-			  const void *ns)
+			  const struct ns_common *ns)
 {
 	struct subsys_private *sp = class_to_subsys(cls);
 
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 09b98f02f559..0613de0fbe44 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2570,15 +2570,14 @@ static void device_release(struct kobject *kobj)
 	kfree(p);
 }
 
-static const void *device_namespace(const struct kobject *kobj)
+static const struct ns_common *device_namespace(const struct kobject *kobj)
 {
 	const struct device *dev = kobj_to_dev(kobj);
-	const void *ns = NULL;
 
 	if (dev->class && dev->class->namespace)
-		ns = dev->class->namespace(dev);
+		return dev->class->namespace(dev);
 
-	return ns;
+	return NULL;
 }
 
 static void device_get_ownership(const struct kobject *kobj, kuid_t *uid, kgid_t *gid)
diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index 558b73940d66..7945614be36d 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -509,12 +509,13 @@ static int ib_device_uevent(const struct device *device,
 	return 0;
 }
 
-static const void *net_namespace(const struct device *d)
+static const struct ns_common *net_namespace(const struct device *d)
 {
 	const struct ib_core_device *coredev =
 			container_of(d, struct ib_core_device, dev);
+	struct net *net = read_pnet(&coredev->rdma_net);
 
-	return read_pnet(&coredev->rdma_net);
+	return net ? to_ns_common(net) : NULL;
 }
 
 static struct class ib_class = {
diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 30339dcabb4d..b58868e1cf11 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -43,6 +43,7 @@
 #include <linux/jiffies.h>
 #include <linux/lockdep.h>
 #include <linux/inet.h>
+#include <net/net_namespace.h>
 #include <rdma/ib_cache.h>
 
 #include <linux/atomic.h>
@@ -1048,7 +1049,7 @@ static void srp_remove_target(struct srp_target_port *target)
 	scsi_remove_host(target->scsi_host);
 	srp_stop_rport_timers(target->rport);
 	srp_disconnect_target(target);
-	kobj_ns_drop(KOBJ_NS_TYPE_NET, target->net);
+	kobj_ns_drop(KOBJ_NS_TYPE_NET, to_ns_common(target->net));
 	for (i = 0; i < target->ch_count; i++) {
 		ch = &target->ch[i];
 		srp_free_ch_ib(target, ch);
@@ -3713,7 +3714,7 @@ static ssize_t add_target_store(struct device *dev,
 
 	target = host_to_target(target_host);
 
-	target->net		= kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+	target->net		= to_net_ns(kobj_ns_grab_current(KOBJ_NS_TYPE_NET));
 	target->io_class	= SRP_REV16A_IB_IO_CLASS;
 	target->scsi_host	= target_host;
 	target->srp_host	= host;
@@ -3905,7 +3906,7 @@ put:
 		 * earlier in this function.
 		 */
 		if (target->state != SRP_TARGET_REMOVED)
-			kobj_ns_drop(KOBJ_NS_TYPE_NET, target->net);
+			kobj_ns_drop(KOBJ_NS_TYPE_NET, to_ns_common(target->net));
 		scsi_host_put(target->scsi_host);
 	}
 
diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index 9a75ad3181ab..eaba44c76a5e 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -808,7 +808,7 @@ int __net_init bond_create_sysfs(struct bond_net *bn)
 	sysfs_attr_init(&bn->class_attr_bonding_masters.attr);
 
 	ret = netdev_class_create_file_ns(&bn->class_attr_bonding_masters,
-					  bn->net);
+					  to_ns_common(bn->net));
 	/* Permit multiple loads of the module by ignoring failures to
 	 * create the bonding_masters sysfs file.  Bonding devices
 	 * created by second or subsequent loads of the module will
@@ -835,7 +835,7 @@ int __net_init bond_create_sysfs(struct bond_net *bn)
 /* Remove /sys/class/net/bonding_masters. */
 void __net_exit bond_destroy_sysfs(struct bond_net *bn)
 {
-	netdev_class_remove_file_ns(&bn->class_attr_bonding_masters, bn->net);
+	netdev_class_remove_file_ns(&bn->class_attr_bonding_masters, to_ns_common(bn->net));
 }
 
 /* Initialize sysfs for each bond.  This sets up and registers
diff --git a/drivers/net/ipvlan/ipvtap.c b/drivers/net/ipvlan/ipvtap.c
index edd13916831a..2d6bbddd1edd 100644
--- a/drivers/net/ipvlan/ipvtap.c
+++ b/drivers/net/ipvlan/ipvtap.c
@@ -30,10 +30,11 @@
 static dev_t ipvtap_major;
 static struct cdev ipvtap_cdev;
 
-static const void *ipvtap_net_namespace(const struct device *d)
+static const struct ns_common *ipvtap_net_namespace(const struct device *d)
 {
 	const struct net_device *dev = to_net_dev(d->parent);
-	return dev_net(dev);
+
+	return to_ns_common(dev_net(dev));
 }
 
 static struct class ipvtap_class = {
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index b391a0f740a3..cc975dfb7380 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -35,10 +35,11 @@ struct macvtap_dev {
  */
 static dev_t macvtap_major;
 
-static const void *macvtap_net_namespace(const struct device *d)
+static const struct ns_common *macvtap_net_namespace(const struct device *d)
 {
 	const struct net_device *dev = to_net_dev(d->parent);
-	return dev_net(dev);
+
+	return to_ns_common(dev_net(dev));
 }
 
 static struct class macvtap_class = {