Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

1 files changed, 670 insertions, 0 deletions

diff --git a/security/tomoyo/gc.c b/security/tomoyo/gc.c
new file mode 100644
index 000000000..026e29ea3
--- /dev/null
+++ b/security/tomoyo/gc.c
@@ -0,0 +1,670 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * security/tomoyo/gc.c
+ *
+ * Copyright (C) 2005-2011  NTT DATA CORPORATION
+ */
+
+#include "common.h"
+#include <linux/kthread.h>
+#include <linux/slab.h>
+
+/**
+ * tomoyo_memory_free - Free memory for elements.
+ *
+ * @ptr:  Pointer to allocated memory.
+ *
+ * Returns nothing.
+ *
+ * Caller holds tomoyo_policy_lock mutex.
+ */
+static inline void tomoyo_memory_free(void *ptr)
+{
+	tomoyo_memory_used[TOMOYO_MEMORY_POLICY] -= ksize(ptr);
+	kfree(ptr);
+}
+
+/* The list for "struct tomoyo_io_buffer". */
+static LIST_HEAD(tomoyo_io_buffer_list);
+/* Lock for protecting tomoyo_io_buffer_list. */
+static DEFINE_SPINLOCK(tomoyo_io_buffer_list_lock);
+
+/**
+ * tomoyo_struct_used_by_io_buffer - Check whether the list element is used by /sys/kernel/security/tomoyo/ users or not.
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns true if @element is used by /sys/kernel/security/tomoyo/ users,
+ * false otherwise.
+ */
+static bool tomoyo_struct_used_by_io_buffer(const struct list_head *element)
+{
+	struct tomoyo_io_buffer *head;
+	bool in_use = false;
+
+	spin_lock(&tomoyo_io_buffer_list_lock);
+	list_for_each_entry(head, &tomoyo_io_buffer_list, list) {
+		head->users++;
+		spin_unlock(&tomoyo_io_buffer_list_lock);
+		mutex_lock(&head->io_sem);
+		if (head->r.domain == element || head->r.group == element ||
+		    head->r.acl == element || &head->w.domain->list == element)
+			in_use = true;
+		mutex_unlock(&head->io_sem);
+		spin_lock(&tomoyo_io_buffer_list_lock);
+		head->users--;
+		if (in_use)
+			break;
+	}
+	spin_unlock(&tomoyo_io_buffer_list_lock);
+	return in_use;
+}
+
+/**
+ * tomoyo_name_used_by_io_buffer - Check whether the string is used by /sys/kernel/security/tomoyo/ users or not.
+ *
+ * @string: String to check.
+ *
+ * Returns true if @string is used by /sys/kernel/security/tomoyo/ users,
+ * false otherwise.
+ */
+static bool tomoyo_name_used_by_io_buffer(const char *string)
+{
+	struct tomoyo_io_buffer *head;
+	const size_t size = strlen(string) + 1;
+	bool in_use = false;
+
+	spin_lock(&tomoyo_io_buffer_list_lock);
+	list_for_each_entry(head, &tomoyo_io_buffer_list, list) {
+		int i;
+
+		head->users++;
+		spin_unlock(&tomoyo_io_buffer_list_lock);
+		mutex_lock(&head->io_sem);
+		for (i = 0; i < TOMOYO_MAX_IO_READ_QUEUE; i++) {
+			const char *w = head->r.w[i];
+
+			if (w < string || w > string + size)
+				continue;
+			in_use = true;
+			break;
+		}
+		mutex_unlock(&head->io_sem);
+		spin_lock(&tomoyo_io_buffer_list_lock);
+		head->users--;
+		if (in_use)
+			break;
+	}
+	spin_unlock(&tomoyo_io_buffer_list_lock);
+	return in_use;
+}
+
+/**
+ * tomoyo_del_transition_control - Delete members in "struct tomoyo_transition_control".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_transition_control(struct list_head *element)
+{
+	struct tomoyo_transition_control *ptr =
+		container_of(element, typeof(*ptr), head.list);
+
+	tomoyo_put_name(ptr->domainname);
+	tomoyo_put_name(ptr->program);
+}
+
+/**
+ * tomoyo_del_aggregator - Delete members in "struct tomoyo_aggregator".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_aggregator(struct list_head *element)
+{
+	struct tomoyo_aggregator *ptr =
+		container_of(element, typeof(*ptr), head.list);
+
+	tomoyo_put_name(ptr->original_name);
+	tomoyo_put_name(ptr->aggregated_name);
+}
+
+/**
+ * tomoyo_del_manager - Delete members in "struct tomoyo_manager".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_manager(struct list_head *element)
+{
+	struct tomoyo_manager *ptr =
+		container_of(element, typeof(*ptr), head.list);
+
+	tomoyo_put_name(ptr->manager);
+}
+
+/**
+ * tomoyo_del_acl - Delete members in "struct tomoyo_acl_info".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static void tomoyo_del_acl(struct list_head *element)
+{
+	struct tomoyo_acl_info *acl =
+		container_of(element, typeof(*acl), list);
+
+	tomoyo_put_condition(acl->cond);
+	switch (acl->type) {
+	case TOMOYO_TYPE_PATH_ACL:
+		{
+			struct tomoyo_path_acl *entry
+				= container_of(acl, typeof(*entry), head);
+			tomoyo_put_name_union(&entry->name);
+		}
+		break;
+	case TOMOYO_TYPE_PATH2_ACL:
+		{
+			struct tomoyo_path2_acl *entry
+				= container_of(acl, typeof(*entry), head);
+			tomoyo_put_name_union(&entry->name1);
+			tomoyo_put_name_union(&entry->name2);
+		}
+		break;
+	case TOMOYO_TYPE_PATH_NUMBER_ACL:
+		{
+			struct tomoyo_path_number_acl *entry
+				= container_of(acl, typeof(*entry), head);
+			tomoyo_put_name_union(&entry->name);
+			tomoyo_put_number_union(&entry->number);
+		}
+		break;
+	case TOMOYO_TYPE_MKDEV_ACL:
+		{
+			struct tomoyo_mkdev_acl *entry
+				= container_of(acl, typeof(*entry), head);
+			tomoyo_put_name_union(&entry->name);
+			tomoyo_put_number_union(&entry->mode);
+			tomoyo_put_number_union(&entry->major);
+			tomoyo_put_number_union(&entry->minor);
+		}
+		break;
+	case TOMOYO_TYPE_MOUNT_ACL:
+		{
+			struct tomoyo_mount_acl *entry
+				= container_of(acl, typeof(*entry), head);
+			tomoyo_put_name_union(&entry->dev_name);
+			tomoyo_put_name_union(&entry->dir_name);
+			tomoyo_put_name_union(&entry->fs_type);
+			tomoyo_put_number_union(&entry->flags);
+		}
+		break;
+	case TOMOYO_TYPE_ENV_ACL:
+		{
+			struct tomoyo_env_acl *entry =
+				container_of(acl, typeof(*entry), head);
+
+			tomoyo_put_name(entry->env);
+		}
+		break;
+	case TOMOYO_TYPE_INET_ACL:
+		{
+			struct tomoyo_inet_acl *entry =
+				container_of(acl, typeof(*entry), head);
+
+			tomoyo_put_group(entry->address.group);
+			tomoyo_put_number_union(&entry->port);
+		}
+		break;
+	case TOMOYO_TYPE_UNIX_ACL:
+		{
+			struct tomoyo_unix_acl *entry =
+				container_of(acl, typeof(*entry), head);
+
+			tomoyo_put_name_union(&entry->name);
+		}
+		break;
+	case TOMOYO_TYPE_MANUAL_TASK_ACL:
+		{
+			struct tomoyo_task_acl *entry =
+				container_of(acl, typeof(*entry), head);
+
+			tomoyo_put_name(entry->domainname);
+		}
+		break;
+	}
+}
+
+/**
+ * tomoyo_del_domain - Delete members in "struct tomoyo_domain_info".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ *
+ * Caller holds tomoyo_policy_lock mutex.
+ */
+static inline void tomoyo_del_domain(struct list_head *element)
+{
+	struct tomoyo_domain_info *domain =
+		container_of(element, typeof(*domain), list);
+	struct tomoyo_acl_info *acl;
+	struct tomoyo_acl_info *tmp;
+
+	/*
+	 * Since this domain is referenced from neither
+	 * "struct tomoyo_io_buffer" nor "struct cred"->security, we can delete
+	 * elements without checking for is_deleted flag.
+	 */
+	list_for_each_entry_safe(acl, tmp, &domain->acl_info_list, list) {
+		tomoyo_del_acl(&acl->list);
+		tomoyo_memory_free(acl);
+	}
+	tomoyo_put_name(domain->domainname);
+}
+
+/**
+ * tomoyo_del_condition - Delete members in "struct tomoyo_condition".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+void tomoyo_del_condition(struct list_head *element)
+{
+	struct tomoyo_condition *cond = container_of(element, typeof(*cond),
+						     head.list);
+	const u16 condc = cond->condc;
+	const u16 numbers_count = cond->numbers_count;
+	const u16 names_count = cond->names_count;
+	const u16 argc = cond->argc;
+	const u16 envc = cond->envc;
+	unsigned int i;
+	const struct tomoyo_condition_element *condp
+		= (const struct tomoyo_condition_element *) (cond + 1);
+	struct tomoyo_number_union *numbers_p
+		= (struct tomoyo_number_union *) (condp + condc);
+	struct tomoyo_name_union *names_p
+		= (struct tomoyo_name_union *) (numbers_p + numbers_count);
+	const struct tomoyo_argv *argv
+		= (const struct tomoyo_argv *) (names_p + names_count);
+	const struct tomoyo_envp *envp
+		= (const struct tomoyo_envp *) (argv + argc);
+
+	for (i = 0; i < numbers_count; i++)
+		tomoyo_put_number_union(numbers_p++);
+	for (i = 0; i < names_count; i++)
+		tomoyo_put_name_union(names_p++);
+	for (i = 0; i < argc; argv++, i++)
+		tomoyo_put_name(argv->value);
+	for (i = 0; i < envc; envp++, i++) {
+		tomoyo_put_name(envp->name);
+		tomoyo_put_name(envp->value);
+	}
+}
+
+/**
+ * tomoyo_del_name - Delete members in "struct tomoyo_name".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_name(struct list_head *element)
+{
+	/* Nothing to do. */
+}
+
+/**
+ * tomoyo_del_path_group - Delete members in "struct tomoyo_path_group".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_path_group(struct list_head *element)
+{
+	struct tomoyo_path_group *member =
+		container_of(element, typeof(*member), head.list);
+
+	tomoyo_put_name(member->member_name);
+}
+
+/**
+ * tomoyo_del_group - Delete "struct tomoyo_group".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_group(struct list_head *element)
+{
+	struct tomoyo_group *group =
+		container_of(element, typeof(*group), head.list);
+
+	tomoyo_put_name(group->group_name);
+}
+
+/**
+ * tomoyo_del_address_group - Delete members in "struct tomoyo_address_group".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_address_group(struct list_head *element)
+{
+	/* Nothing to do. */
+}
+
+/**
+ * tomoyo_del_number_group - Delete members in "struct tomoyo_number_group".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_number_group(struct list_head *element)
+{
+	/* Nothing to do. */
+}
+
+/**
+ * tomoyo_try_to_gc - Try to kfree() an entry.
+ *
+ * @type:    One of values in "enum tomoyo_policy_id".
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ *
+ * Caller holds tomoyo_policy_lock mutex.
+ */
+static void tomoyo_try_to_gc(const enum tomoyo_policy_id type,
+			     struct list_head *element)
+{
+	/*
+	 * __list_del_entry() guarantees that the list element became no longer
+	 * reachable from the list which the element was originally on (e.g.
+	 * tomoyo_domain_list). Also, synchronize_srcu() guarantees that the
+	 * list element became no longer referenced by syscall users.
+	 */
+	__list_del_entry(element);
+	mutex_unlock(&tomoyo_policy_lock);
+	synchronize_srcu(&tomoyo_ss);
+	/*
+	 * However, there are two users which may still be using the list
+	 * element. We need to defer until both users forget this element.
+	 *
+	 * Don't kfree() until "struct tomoyo_io_buffer"->r.{domain,group,acl}
+	 * and "struct tomoyo_io_buffer"->w.domain forget this element.
+	 */
+	if (tomoyo_struct_used_by_io_buffer(element))
+		goto reinject;
+	switch (type) {
+	case TOMOYO_ID_TRANSITION_CONTROL:
+		tomoyo_del_transition_control(element);
+		break;
+	case TOMOYO_ID_MANAGER:
+		tomoyo_del_manager(element);
+		break;
+	case TOMOYO_ID_AGGREGATOR:
+		tomoyo_del_aggregator(element);
+		break;
+	case TOMOYO_ID_GROUP:
+		tomoyo_del_group(element);
+		break;
+	case TOMOYO_ID_PATH_GROUP:
+		tomoyo_del_path_group(element);
+		break;
+	case TOMOYO_ID_ADDRESS_GROUP:
+		tomoyo_del_address_group(element);
+		break;
+	case TOMOYO_ID_NUMBER_GROUP:
+		tomoyo_del_number_group(element);
+		break;
+	case TOMOYO_ID_CONDITION:
+		tomoyo_del_condition(element);
+		break;
+	case TOMOYO_ID_NAME:
+		/*
+		 * Don't kfree() until all "struct tomoyo_io_buffer"->r.w[]
+		 * forget this element.
+		 */
+		if (tomoyo_name_used_by_io_buffer
+		    (container_of(element, typeof(struct tomoyo_name),
+				  head.list)->entry.name))
+			goto reinject;
+		tomoyo_del_name(element);
+		break;
+	case TOMOYO_ID_ACL:
+		tomoyo_del_acl(element);
+		break;
+	case TOMOYO_ID_DOMAIN:
+		/*
+		 * Don't kfree() until all "struct cred"->security forget this
+		 * element.
+		 */
+		if (atomic_read(&container_of
+				(element, typeof(struct tomoyo_domain_info),
+				 list)->users))
+			goto reinject;
+		break;
+	case TOMOYO_MAX_POLICY:
+		break;
+	}
+	mutex_lock(&tomoyo_policy_lock);
+	if (type == TOMOYO_ID_DOMAIN)
+		tomoyo_del_domain(element);
+	tomoyo_memory_free(element);
+	return;
+reinject:
+	/*
+	 * We can safely reinject this element here because
+	 * (1) Appending list elements and removing list elements are protected
+	 *     by tomoyo_policy_lock mutex.
+	 * (2) Only this function removes list elements and this function is
+	 *     exclusively executed by tomoyo_gc_mutex mutex.
+	 * are true.
+	 */
+	mutex_lock(&tomoyo_policy_lock);
+	list_add_rcu(element, element->prev);
+}
+
+/**
+ * tomoyo_collect_member - Delete elements with "struct tomoyo_acl_head".
+ *
+ * @id:          One of values in "enum tomoyo_policy_id".
+ * @member_list: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static void tomoyo_collect_member(const enum tomoyo_policy_id id,
+				  struct list_head *member_list)
+{
+	struct tomoyo_acl_head *member;
+	struct tomoyo_acl_head *tmp;
+
+	list_for_each_entry_safe(member, tmp, member_list, list) {
+		if (!member->is_deleted)
+			continue;
+		member->is_deleted = TOMOYO_GC_IN_PROGRESS;
+		tomoyo_try_to_gc(id, &member->list);
+	}
+}
+
+/**
+ * tomoyo_collect_acl - Delete elements in "struct tomoyo_domain_info".
+ *
+ * @list: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static void tomoyo_collect_acl(struct list_head *list)
+{
+	struct tomoyo_acl_info *acl;
+	struct tomoyo_acl_info *tmp;
+
+	list_for_each_entry_safe(acl, tmp, list, list) {
+		if (!acl->is_deleted)
+			continue;
+		acl->is_deleted = TOMOYO_GC_IN_PROGRESS;
+		tomoyo_try_to_gc(TOMOYO_ID_ACL, &acl->list);
+	}
+}
+
+/**
+ * tomoyo_collect_entry - Try to kfree() deleted elements.
+ *
+ * Returns nothing.
+ */
+static void tomoyo_collect_entry(void)
+{
+	int i;
+	enum tomoyo_policy_id id;
+	struct tomoyo_policy_namespace *ns;
+
+	mutex_lock(&tomoyo_policy_lock);
+	{
+		struct tomoyo_domain_info *domain;
+		struct tomoyo_domain_info *tmp;
+
+		list_for_each_entry_safe(domain, tmp, &tomoyo_domain_list,
+					 list) {
+			tomoyo_collect_acl(&domain->acl_info_list);
+			if (!domain->is_deleted || atomic_read(&domain->users))
+				continue;
+			tomoyo_try_to_gc(TOMOYO_ID_DOMAIN, &domain->list);
+		}
+	}
+	list_for_each_entry(ns, &tomoyo_namespace_list, namespace_list) {
+		for (id = 0; id < TOMOYO_MAX_POLICY; id++)
+			tomoyo_collect_member(id, &ns->policy_list[id]);
+		for (i = 0; i < TOMOYO_MAX_ACL_GROUPS; i++)
+			tomoyo_collect_acl(&ns->acl_group[i]);
+	}
+	{
+		struct tomoyo_shared_acl_head *ptr;
+		struct tomoyo_shared_acl_head *tmp;
+
+		list_for_each_entry_safe(ptr, tmp, &tomoyo_condition_list,
+					 list) {
+			if (atomic_read(&ptr->users) > 0)
+				continue;
+			atomic_set(&ptr->users, TOMOYO_GC_IN_PROGRESS);
+			tomoyo_try_to_gc(TOMOYO_ID_CONDITION, &ptr->list);
+		}
+	}
+	list_for_each_entry(ns, &tomoyo_namespace_list, namespace_list) {
+		for (i = 0; i < TOMOYO_MAX_GROUP; i++) {
+			struct list_head *list = &ns->group_list[i];
+			struct tomoyo_group *group;
+			struct tomoyo_group *tmp;
+
+			switch (i) {
+			case 0:
+				id = TOMOYO_ID_PATH_GROUP;
+				break;
+			case 1:
+				id = TOMOYO_ID_NUMBER_GROUP;
+				break;
+			default:
+				id = TOMOYO_ID_ADDRESS_GROUP;
+				break;
+			}
+			list_for_each_entry_safe(group, tmp, list, head.list) {
+				tomoyo_collect_member(id, &group->member_list);
+				if (!list_empty(&group->member_list) ||
+				    atomic_read(&group->head.users) > 0)
+					continue;
+				atomic_set(&group->head.users,
+					   TOMOYO_GC_IN_PROGRESS);
+				tomoyo_try_to_gc(TOMOYO_ID_GROUP,
+						 &group->head.list);
+			}
+		}
+	}
+	for (i = 0; i < TOMOYO_MAX_HASH; i++) {
+		struct list_head *list = &tomoyo_name_list[i];
+		struct tomoyo_shared_acl_head *ptr;
+		struct tomoyo_shared_acl_head *tmp;
+
+		list_for_each_entry_safe(ptr, tmp, list, list) {
+			if (atomic_read(&ptr->users) > 0)
+				continue;
+			atomic_set(&ptr->users, TOMOYO_GC_IN_PROGRESS);
+			tomoyo_try_to_gc(TOMOYO_ID_NAME, &ptr->list);
+		}
+	}
+	mutex_unlock(&tomoyo_policy_lock);
+}
+
+/**
+ * tomoyo_gc_thread - Garbage collector thread function.
+ *
+ * @unused: Unused.
+ *
+ * Returns 0.
+ */
+static int tomoyo_gc_thread(void *unused)
+{
+	/* Garbage collector thread is exclusive. */
+	static DEFINE_MUTEX(tomoyo_gc_mutex);
+
+	if (!mutex_trylock(&tomoyo_gc_mutex))
+		goto out;
+	tomoyo_collect_entry();
+	{
+		struct tomoyo_io_buffer *head;
+		struct tomoyo_io_buffer *tmp;
+
+		spin_lock(&tomoyo_io_buffer_list_lock);
+		list_for_each_entry_safe(head, tmp, &tomoyo_io_buffer_list,
+					 list) {
+			if (head->users)
+				continue;
+			list_del(&head->list);
+			kfree(head->read_buf);
+			kfree(head->write_buf);
+			kfree(head);
+		}
+		spin_unlock(&tomoyo_io_buffer_list_lock);
+	}
+	mutex_unlock(&tomoyo_gc_mutex);
+out:
+	/* This acts as do_exit(0). */
+	return 0;
+}
+
+/**
+ * tomoyo_notify_gc - Register/unregister /sys/kernel/security/tomoyo/ users.
+ *
+ * @head:        Pointer to "struct tomoyo_io_buffer".
+ * @is_register: True if register, false if unregister.
+ *
+ * Returns nothing.
+ */
+void tomoyo_notify_gc(struct tomoyo_io_buffer *head, const bool is_register)
+{
+	bool is_write = false;
+
+	spin_lock(&tomoyo_io_buffer_list_lock);
+	if (is_register) {
+		head->users = 1;
+		list_add(&head->list, &tomoyo_io_buffer_list);
+	} else {
+		is_write = head->write_buf != NULL;
+		if (!--head->users) {
+			list_del(&head->list);
+			kfree(head->read_buf);
+			kfree(head->write_buf);
+			kfree(head);
+		}
+	}
+	spin_unlock(&tomoyo_io_buffer_list_lock);
+	if (is_write)
+		kthread_run(tomoyo_gc_thread, NULL, "GC for TOMOYO");
+}