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, 1311 insertions, 0 deletions

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
new file mode 100644
index 000000000..adcea0fe7
--- /dev/null
+++ b/security/landlock/fs.c
@@ -0,0 +1,1311 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Filesystem management and hooks
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ * Copyright © 2021-2022 Microsoft Corporation
+ */
+
+#include <linux/atomic.h>
+#include <linux/bitops.h>
+#include <linux/bits.h>
+#include <linux/compiler_types.h>
+#include <linux/dcache.h>
+#include <linux/err.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/list.h>
+#include <linux/lsm_hooks.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/path.h>
+#include <linux/rcupdate.h>
+#include <linux/spinlock.h>
+#include <linux/stat.h>
+#include <linux/types.h>
+#include <linux/wait_bit.h>
+#include <linux/workqueue.h>
+#include <uapi/linux/landlock.h>
+
+#include "common.h"
+#include "cred.h"
+#include "fs.h"
+#include "limits.h"
+#include "object.h"
+#include "ruleset.h"
+#include "setup.h"
+
+/* Underlying object management */
+
+static void release_inode(struct landlock_object *const object)
+	__releases(object->lock)
+{
+	struct inode *const inode = object->underobj;
+	struct super_block *sb;
+
+	if (!inode) {
+		spin_unlock(&object->lock);
+		return;
+	}
+
+	/*
+	 * Protects against concurrent use by hook_sb_delete() of the reference
+	 * to the underlying inode.
+	 */
+	object->underobj = NULL;
+	/*
+	 * Makes sure that if the filesystem is concurrently unmounted,
+	 * hook_sb_delete() will wait for us to finish iput().
+	 */
+	sb = inode->i_sb;
+	atomic_long_inc(&landlock_superblock(sb)->inode_refs);
+	spin_unlock(&object->lock);
+	/*
+	 * Because object->underobj was not NULL, hook_sb_delete() and
+	 * get_inode_object() guarantee that it is safe to reset
+	 * landlock_inode(inode)->object while it is not NULL.  It is therefore
+	 * not necessary to lock inode->i_lock.
+	 */
+	rcu_assign_pointer(landlock_inode(inode)->object, NULL);
+	/*
+	 * Now, new rules can safely be tied to @inode with get_inode_object().
+	 */
+
+	iput(inode);
+	if (atomic_long_dec_and_test(&landlock_superblock(sb)->inode_refs))
+		wake_up_var(&landlock_superblock(sb)->inode_refs);
+}
+
+static const struct landlock_object_underops landlock_fs_underops = {
+	.release = release_inode
+};
+
+/* Ruleset management */
+
+static struct landlock_object *get_inode_object(struct inode *const inode)
+{
+	struct landlock_object *object, *new_object;
+	struct landlock_inode_security *inode_sec = landlock_inode(inode);
+
+	rcu_read_lock();
+retry:
+	object = rcu_dereference(inode_sec->object);
+	if (object) {
+		if (likely(refcount_inc_not_zero(&object->usage))) {
+			rcu_read_unlock();
+			return object;
+		}
+		/*
+		 * We are racing with release_inode(), the object is going
+		 * away.  Wait for release_inode(), then retry.
+		 */
+		spin_lock(&object->lock);
+		spin_unlock(&object->lock);
+		goto retry;
+	}
+	rcu_read_unlock();
+
+	/*
+	 * If there is no object tied to @inode, then create a new one (without
+	 * holding any locks).
+	 */
+	new_object = landlock_create_object(&landlock_fs_underops, inode);
+	if (IS_ERR(new_object))
+		return new_object;
+
+	/*
+	 * Protects against concurrent calls to get_inode_object() or
+	 * hook_sb_delete().
+	 */
+	spin_lock(&inode->i_lock);
+	if (unlikely(rcu_access_pointer(inode_sec->object))) {
+		/* Someone else just created the object, bail out and retry. */
+		spin_unlock(&inode->i_lock);
+		kfree(new_object);
+
+		rcu_read_lock();
+		goto retry;
+	}
+
+	/*
+	 * @inode will be released by hook_sb_delete() on its superblock
+	 * shutdown, or by release_inode() when no more ruleset references the
+	 * related object.
+	 */
+	ihold(inode);
+	rcu_assign_pointer(inode_sec->object, new_object);
+	spin_unlock(&inode->i_lock);
+	return new_object;
+}
+
+/* All access rights that can be tied to files. */
+/* clang-format off */
+#define ACCESS_FILE ( \
+	LANDLOCK_ACCESS_FS_EXECUTE | \
+	LANDLOCK_ACCESS_FS_WRITE_FILE | \
+	LANDLOCK_ACCESS_FS_READ_FILE | \
+	LANDLOCK_ACCESS_FS_TRUNCATE)
+/* clang-format on */
+
+/*
+ * All access rights that are denied by default whether they are handled or not
+ * by a ruleset/layer.  This must be ORed with all ruleset->fs_access_masks[]
+ * entries when we need to get the absolute handled access masks.
+ */
+/* clang-format off */
+#define ACCESS_INITIALLY_DENIED ( \
+	LANDLOCK_ACCESS_FS_REFER)
+/* clang-format on */
+
+/*
+ * @path: Should have been checked by get_path_from_fd().
+ */
+int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
+			    const struct path *const path,
+			    access_mask_t access_rights)
+{
+	int err;
+	struct landlock_object *object;
+
+	/* Files only get access rights that make sense. */
+	if (!d_is_dir(path->dentry) &&
+	    (access_rights | ACCESS_FILE) != ACCESS_FILE)
+		return -EINVAL;
+	if (WARN_ON_ONCE(ruleset->num_layers != 1))
+		return -EINVAL;
+
+	/* Transforms relative access rights to absolute ones. */
+	access_rights |=
+		LANDLOCK_MASK_ACCESS_FS &
+		~(ruleset->fs_access_masks[0] | ACCESS_INITIALLY_DENIED);
+	object = get_inode_object(d_backing_inode(path->dentry));
+	if (IS_ERR(object))
+		return PTR_ERR(object);
+	mutex_lock(&ruleset->lock);
+	err = landlock_insert_rule(ruleset, object, access_rights);
+	mutex_unlock(&ruleset->lock);
+	/*
+	 * No need to check for an error because landlock_insert_rule()
+	 * increments the refcount for the new object if needed.
+	 */
+	landlock_put_object(object);
+	return err;
+}
+
+/* Access-control management */
+
+/*
+ * The lifetime of the returned rule is tied to @domain.
+ *
+ * Returns NULL if no rule is found or if @dentry is negative.
+ */
+static inline const struct landlock_rule *
+find_rule(const struct landlock_ruleset *const domain,
+	  const struct dentry *const dentry)
+{
+	const struct landlock_rule *rule;
+	const struct inode *inode;
+
+	/* Ignores nonexistent leafs. */
+	if (d_is_negative(dentry))
+		return NULL;
+
+	inode = d_backing_inode(dentry);
+	rcu_read_lock();
+	rule = landlock_find_rule(
+		domain, rcu_dereference(landlock_inode(inode)->object));
+	rcu_read_unlock();
+	return rule;
+}
+
+/*
+ * @layer_masks is read and may be updated according to the access request and
+ * the matching rule.
+ *
+ * Returns true if the request is allowed (i.e. relevant layer masks for the
+ * request are empty).
+ */
+static inline bool
+unmask_layers(const struct landlock_rule *const rule,
+	      const access_mask_t access_request,
+	      layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+{
+	size_t layer_level;
+
+	if (!access_request || !layer_masks)
+		return true;
+	if (!rule)
+		return false;
+
+	/*
+	 * An access is granted if, for each policy layer, at least one rule
+	 * encountered on the pathwalk grants the requested access,
+	 * regardless of its position in the layer stack.  We must then check
+	 * the remaining layers for each inode, from the first added layer to
+	 * the last one.  When there is multiple requested accesses, for each
+	 * policy layer, the full set of requested accesses may not be granted
+	 * by only one rule, but by the union (binary OR) of multiple rules.
+	 * E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
+	 */
+	for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
+		const struct landlock_layer *const layer =
+			&rule->layers[layer_level];
+		const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
+		const unsigned long access_req = access_request;
+		unsigned long access_bit;
+		bool is_empty;
+
+		/*
+		 * Records in @layer_masks which layer grants access to each
+		 * requested access.
+		 */
+		is_empty = true;
+		for_each_set_bit(access_bit, &access_req,
+				 ARRAY_SIZE(*layer_masks)) {
+			if (layer->access & BIT_ULL(access_bit))
+				(*layer_masks)[access_bit] &= ~layer_bit;
+			is_empty = is_empty && !(*layer_masks)[access_bit];
+		}
+		if (is_empty)
+			return true;
+	}
+	return false;
+}
+
+/*
+ * Allows access to pseudo filesystems that will never be mountable (e.g.
+ * sockfs, pipefs), but can still be reachable through
+ * /proc/<pid>/fd/<file-descriptor>
+ */
+static inline bool is_nouser_or_private(const struct dentry *dentry)
+{
+	return (dentry->d_sb->s_flags & SB_NOUSER) ||
+	       (d_is_positive(dentry) &&
+		unlikely(IS_PRIVATE(d_backing_inode(dentry))));
+}
+
+static inline access_mask_t
+get_handled_accesses(const struct landlock_ruleset *const domain)
+{
+	access_mask_t access_dom = ACCESS_INITIALLY_DENIED;
+	size_t layer_level;
+
+	for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
+		access_dom |= domain->fs_access_masks[layer_level];
+	return access_dom & LANDLOCK_MASK_ACCESS_FS;
+}
+
+/**
+ * init_layer_masks - Initialize layer masks from an access request
+ *
+ * Populates @layer_masks such that for each access right in @access_request,
+ * the bits for all the layers are set where this access right is handled.
+ *
+ * @domain: The domain that defines the current restrictions.
+ * @access_request: The requested access rights to check.
+ * @layer_masks: The layer masks to populate.
+ *
+ * Returns: An access mask where each access right bit is set which is handled
+ * in any of the active layers in @domain.
+ */
+static inline access_mask_t
+init_layer_masks(const struct landlock_ruleset *const domain,
+		 const access_mask_t access_request,
+		 layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+{
+	access_mask_t handled_accesses = 0;
+	size_t layer_level;
+
+	memset(layer_masks, 0, sizeof(*layer_masks));
+	/* An empty access request can happen because of O_WRONLY | O_RDWR. */
+	if (!access_request)
+		return 0;
+
+	/* Saves all handled accesses per layer. */
+	for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
+		const unsigned long access_req = access_request;
+		unsigned long access_bit;
+
+		for_each_set_bit(access_bit, &access_req,
+				 ARRAY_SIZE(*layer_masks)) {
+			/*
+			 * Artificially handles all initially denied by default
+			 * access rights.
+			 */
+			if (BIT_ULL(access_bit) &
+			    (domain->fs_access_masks[layer_level] |
+			     ACCESS_INITIALLY_DENIED)) {
+				(*layer_masks)[access_bit] |=
+					BIT_ULL(layer_level);
+				handled_accesses |= BIT_ULL(access_bit);
+			}
+		}
+	}
+	return handled_accesses;
+}
+
+/*
+ * Check that a destination file hierarchy has more restrictions than a source
+ * file hierarchy.  This is only used for link and rename actions.
+ *
+ * @layer_masks_child2: Optional child masks.
+ */
+static inline bool no_more_access(
+	const layer_mask_t (*const layer_masks_parent1)[LANDLOCK_NUM_ACCESS_FS],
+	const layer_mask_t (*const layer_masks_child1)[LANDLOCK_NUM_ACCESS_FS],
+	const bool child1_is_directory,
+	const layer_mask_t (*const layer_masks_parent2)[LANDLOCK_NUM_ACCESS_FS],
+	const layer_mask_t (*const layer_masks_child2)[LANDLOCK_NUM_ACCESS_FS],
+	const bool child2_is_directory)
+{
+	unsigned long access_bit;
+
+	for (access_bit = 0; access_bit < ARRAY_SIZE(*layer_masks_parent2);
+	     access_bit++) {
+		/* Ignores accesses that only make sense for directories. */
+		const bool is_file_access =
+			!!(BIT_ULL(access_bit) & ACCESS_FILE);
+
+		if (child1_is_directory || is_file_access) {
+			/*
+			 * Checks if the destination restrictions are a
+			 * superset of the source ones (i.e. inherited access
+			 * rights without child exceptions):
+			 * restrictions(parent2) >= restrictions(child1)
+			 */
+			if ((((*layer_masks_parent1)[access_bit] &
+			      (*layer_masks_child1)[access_bit]) |
+			     (*layer_masks_parent2)[access_bit]) !=
+			    (*layer_masks_parent2)[access_bit])
+				return false;
+		}
+
+		if (!layer_masks_child2)
+			continue;
+		if (child2_is_directory || is_file_access) {
+			/*
+			 * Checks inverted restrictions for RENAME_EXCHANGE:
+			 * restrictions(parent1) >= restrictions(child2)
+			 */
+			if ((((*layer_masks_parent2)[access_bit] &
+			      (*layer_masks_child2)[access_bit]) |
+			     (*layer_masks_parent1)[access_bit]) !=
+			    (*layer_masks_parent1)[access_bit])
+				return false;
+		}
+	}
+	return true;
+}
+
+/*
+ * Removes @layer_masks accesses that are not requested.
+ *
+ * Returns true if the request is allowed, false otherwise.
+ */
+static inline bool
+scope_to_request(const access_mask_t access_request,
+		 layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+{
+	const unsigned long access_req = access_request;
+	unsigned long access_bit;
+
+	if (WARN_ON_ONCE(!layer_masks))
+		return true;
+
+	for_each_clear_bit(access_bit, &access_req, ARRAY_SIZE(*layer_masks))
+		(*layer_masks)[access_bit] = 0;
+	return !memchr_inv(layer_masks, 0, sizeof(*layer_masks));
+}
+
+/*
+ * Returns true if there is at least one access right different than
+ * LANDLOCK_ACCESS_FS_REFER.
+ */
+static inline bool
+is_eacces(const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS],
+	  const access_mask_t access_request)
+{
+	unsigned long access_bit;
+	/* LANDLOCK_ACCESS_FS_REFER alone must return -EXDEV. */
+	const unsigned long access_check = access_request &
+					   ~LANDLOCK_ACCESS_FS_REFER;
+
+	if (!layer_masks)
+		return false;
+
+	for_each_set_bit(access_bit, &access_check, ARRAY_SIZE(*layer_masks)) {
+		if ((*layer_masks)[access_bit])
+			return true;
+	}
+	return false;
+}
+
+/**
+ * is_access_to_paths_allowed - Check accesses for requests with a common path
+ *
+ * @domain: Domain to check against.
+ * @path: File hierarchy to walk through.
+ * @access_request_parent1: Accesses to check, once @layer_masks_parent1 is
+ *     equal to @layer_masks_parent2 (if any).  This is tied to the unique
+ *     requested path for most actions, or the source in case of a refer action
+ *     (i.e. rename or link), or the source and destination in case of
+ *     RENAME_EXCHANGE.
+ * @layer_masks_parent1: Pointer to a matrix of layer masks per access
+ *     masks, identifying the layers that forbid a specific access.  Bits from
+ *     this matrix can be unset according to the @path walk.  An empty matrix
+ *     means that @domain allows all possible Landlock accesses (i.e. not only
+ *     those identified by @access_request_parent1).  This matrix can
+ *     initially refer to domain layer masks and, when the accesses for the
+ *     destination and source are the same, to requested layer masks.
+ * @dentry_child1: Dentry to the initial child of the parent1 path.  This
+ *     pointer must be NULL for non-refer actions (i.e. not link nor rename).
+ * @access_request_parent2: Similar to @access_request_parent1 but for a
+ *     request involving a source and a destination.  This refers to the
+ *     destination, except in case of RENAME_EXCHANGE where it also refers to
+ *     the source.  Must be set to 0 when using a simple path request.
+ * @layer_masks_parent2: Similar to @layer_masks_parent1 but for a refer
+ *     action.  This must be NULL otherwise.
+ * @dentry_child2: Dentry to the initial child of the parent2 path.  This
+ *     pointer is only set for RENAME_EXCHANGE actions and must be NULL
+ *     otherwise.
+ *
+ * This helper first checks that the destination has a superset of restrictions
+ * compared to the source (if any) for a common path.  Because of
+ * RENAME_EXCHANGE actions, source and destinations may be swapped.  It then
+ * checks that the collected accesses and the remaining ones are enough to
+ * allow the request.
+ *
+ * Returns:
+ * - true if the access request is granted;
+ * - false otherwise.
+ */
+static bool is_access_to_paths_allowed(
+	const struct landlock_ruleset *const domain,
+	const struct path *const path,
+	const access_mask_t access_request_parent1,
+	layer_mask_t (*const layer_masks_parent1)[LANDLOCK_NUM_ACCESS_FS],
+	const struct dentry *const dentry_child1,
+	const access_mask_t access_request_parent2,
+	layer_mask_t (*const layer_masks_parent2)[LANDLOCK_NUM_ACCESS_FS],
+	const struct dentry *const dentry_child2)
+{
+	bool allowed_parent1 = false, allowed_parent2 = false, is_dom_check,
+	     child1_is_directory = true, child2_is_directory = true;
+	struct path walker_path;
+	access_mask_t access_masked_parent1, access_masked_parent2;
+	layer_mask_t _layer_masks_child1[LANDLOCK_NUM_ACCESS_FS],
+		_layer_masks_child2[LANDLOCK_NUM_ACCESS_FS];
+	layer_mask_t(*layer_masks_child1)[LANDLOCK_NUM_ACCESS_FS] = NULL,
+	(*layer_masks_child2)[LANDLOCK_NUM_ACCESS_FS] = NULL;
+
+	if (!access_request_parent1 && !access_request_parent2)
+		return true;
+	if (WARN_ON_ONCE(!domain || !path))
+		return true;
+	if (is_nouser_or_private(path->dentry))
+		return true;
+	if (WARN_ON_ONCE(domain->num_layers < 1 || !layer_masks_parent1))
+		return false;
+
+	if (unlikely(layer_masks_parent2)) {
+		if (WARN_ON_ONCE(!dentry_child1))
+			return false;
+		/*
+		 * For a double request, first check for potential privilege
+		 * escalation by looking at domain handled accesses (which are
+		 * a superset of the meaningful requested accesses).
+		 */
+		access_masked_parent1 = access_masked_parent2 =
+			get_handled_accesses(domain);
+		is_dom_check = true;
+	} else {
+		if (WARN_ON_ONCE(dentry_child1 || dentry_child2))
+			return false;
+		/* For a simple request, only check for requested accesses. */
+		access_masked_parent1 = access_request_parent1;
+		access_masked_parent2 = access_request_parent2;
+		is_dom_check = false;
+	}
+
+	if (unlikely(dentry_child1)) {
+		unmask_layers(find_rule(domain, dentry_child1),
+			      init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
+					       &_layer_masks_child1),
+			      &_layer_masks_child1);
+		layer_masks_child1 = &_layer_masks_child1;
+		child1_is_directory = d_is_dir(dentry_child1);
+	}
+	if (unlikely(dentry_child2)) {
+		unmask_layers(find_rule(domain, dentry_child2),
+			      init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
+					       &_layer_masks_child2),
+			      &_layer_masks_child2);
+		layer_masks_child2 = &_layer_masks_child2;
+		child2_is_directory = d_is_dir(dentry_child2);
+	}
+
+	walker_path = *path;
+	path_get(&walker_path);
+	/*
+	 * We need to walk through all the hierarchy to not miss any relevant
+	 * restriction.
+	 */
+	while (true) {
+		struct dentry *parent_dentry;
+		const struct landlock_rule *rule;
+
+		/*
+		 * If at least all accesses allowed on the destination are
+		 * already allowed on the source, respectively if there is at
+		 * least as much as restrictions on the destination than on the
+		 * source, then we can safely refer files from the source to
+		 * the destination without risking a privilege escalation.
+		 * This also applies in the case of RENAME_EXCHANGE, which
+		 * implies checks on both direction.  This is crucial for
+		 * standalone multilayered security policies.  Furthermore,
+		 * this helps avoid policy writers to shoot themselves in the
+		 * foot.
+		 */
+		if (unlikely(is_dom_check &&
+			     no_more_access(
+				     layer_masks_parent1, layer_masks_child1,
+				     child1_is_directory, layer_masks_parent2,
+				     layer_masks_child2,
+				     child2_is_directory))) {
+			allowed_parent1 = scope_to_request(
+				access_request_parent1, layer_masks_parent1);
+			allowed_parent2 = scope_to_request(
+				access_request_parent2, layer_masks_parent2);
+
+			/* Stops when all accesses are granted. */
+			if (allowed_parent1 && allowed_parent2)
+				break;
+
+			/*
+			 * Now, downgrades the remaining checks from domain
+			 * handled accesses to requested accesses.
+			 */
+			is_dom_check = false;
+			access_masked_parent1 = access_request_parent1;
+			access_masked_parent2 = access_request_parent2;
+		}
+
+		rule = find_rule(domain, walker_path.dentry);
+		allowed_parent1 = unmask_layers(rule, access_masked_parent1,
+						layer_masks_parent1);
+		allowed_parent2 = unmask_layers(rule, access_masked_parent2,
+						layer_masks_parent2);
+
+		/* Stops when a rule from each layer grants access. */
+		if (allowed_parent1 && allowed_parent2)
+			break;
+
+jump_up:
+		if (walker_path.dentry == walker_path.mnt->mnt_root) {
+			if (follow_up(&walker_path)) {
+				/* Ignores hidden mount points. */
+				goto jump_up;
+			} else {
+				/*
+				 * Stops at the real root.  Denies access
+				 * because not all layers have granted access.
+				 */
+				break;
+			}
+		}
+		if (unlikely(IS_ROOT(walker_path.dentry))) {
+			/*
+			 * Stops at disconnected root directories.  Only allows
+			 * access to internal filesystems (e.g. nsfs, which is
+			 * reachable through /proc/<pid>/ns/<namespace>).
+			 */
+			allowed_parent1 = allowed_parent2 =
+				!!(walker_path.mnt->mnt_flags & MNT_INTERNAL);
+			break;
+		}
+		parent_dentry = dget_parent(walker_path.dentry);
+		dput(walker_path.dentry);
+		walker_path.dentry = parent_dentry;
+	}
+	path_put(&walker_path);
+
+	return allowed_parent1 && allowed_parent2;
+}
+
+static inline int check_access_path(const struct landlock_ruleset *const domain,
+				    const struct path *const path,
+				    access_mask_t access_request)
+{
+	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
+
+	access_request = init_layer_masks(domain, access_request, &layer_masks);
+	if (is_access_to_paths_allowed(domain, path, access_request,
+				       &layer_masks, NULL, 0, NULL, NULL))
+		return 0;
+	return -EACCES;
+}
+
+static inline int current_check_access_path(const struct path *const path,
+					    const access_mask_t access_request)
+{
+	const struct landlock_ruleset *const dom =
+		landlock_get_current_domain();
+
+	if (!dom)
+		return 0;
+	return check_access_path(dom, path, access_request);
+}
+
+static inline access_mask_t get_mode_access(const umode_t mode)
+{
+	switch (mode & S_IFMT) {
+	case S_IFLNK:
+		return LANDLOCK_ACCESS_FS_MAKE_SYM;
+	case 0:
+		/* A zero mode translates to S_IFREG. */
+	case S_IFREG:
+		return LANDLOCK_ACCESS_FS_MAKE_REG;
+	case S_IFDIR:
+		return LANDLOCK_ACCESS_FS_MAKE_DIR;
+	case S_IFCHR:
+		return LANDLOCK_ACCESS_FS_MAKE_CHAR;
+	case S_IFBLK:
+		return LANDLOCK_ACCESS_FS_MAKE_BLOCK;
+	case S_IFIFO:
+		return LANDLOCK_ACCESS_FS_MAKE_FIFO;
+	case S_IFSOCK:
+		return LANDLOCK_ACCESS_FS_MAKE_SOCK;
+	default:
+		WARN_ON_ONCE(1);
+		return 0;
+	}
+}
+
+static inline access_mask_t maybe_remove(const struct dentry *const dentry)
+{
+	if (d_is_negative(dentry))
+		return 0;
+	return d_is_dir(dentry) ? LANDLOCK_ACCESS_FS_REMOVE_DIR :
+				  LANDLOCK_ACCESS_FS_REMOVE_FILE;
+}
+
+/**
+ * collect_domain_accesses - Walk through a file path and collect accesses
+ *
+ * @domain: Domain to check against.
+ * @mnt_root: Last directory to check.
+ * @dir: Directory to start the walk from.
+ * @layer_masks_dom: Where to store the collected accesses.
+ *
+ * This helper is useful to begin a path walk from the @dir directory to a
+ * @mnt_root directory used as a mount point.  This mount point is the common
+ * ancestor between the source and the destination of a renamed and linked
+ * file.  While walking from @dir to @mnt_root, we record all the domain's
+ * allowed accesses in @layer_masks_dom.
+ *
+ * This is similar to is_access_to_paths_allowed() but much simpler because it
+ * only handles walking on the same mount point and only checks one set of
+ * accesses.
+ *
+ * Returns:
+ * - true if all the domain access rights are allowed for @dir;
+ * - false if the walk reached @mnt_root.
+ */
+static bool collect_domain_accesses(
+	const struct landlock_ruleset *const domain,
+	const struct dentry *const mnt_root, struct dentry *dir,
+	layer_mask_t (*const layer_masks_dom)[LANDLOCK_NUM_ACCESS_FS])
+{
+	unsigned long access_dom;
+	bool ret = false;
+
+	if (WARN_ON_ONCE(!domain || !mnt_root || !dir || !layer_masks_dom))
+		return true;
+	if (is_nouser_or_private(dir))
+		return true;
+
+	access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
+				      layer_masks_dom);
+
+	dget(dir);
+	while (true) {
+		struct dentry *parent_dentry;
+
+		/* Gets all layers allowing all domain accesses. */
+		if (unmask_layers(find_rule(domain, dir), access_dom,
+				  layer_masks_dom)) {
+			/*
+			 * Stops when all handled accesses are allowed by at
+			 * least one rule in each layer.
+			 */
+			ret = true;
+			break;
+		}
+
+		/* We should not reach a root other than @mnt_root. */
+		if (dir == mnt_root || WARN_ON_ONCE(IS_ROOT(dir)))
+			break;
+
+		parent_dentry = dget_parent(dir);
+		dput(dir);
+		dir = parent_dentry;
+	}
+	dput(dir);
+	return ret;
+}
+
+/**
+ * current_check_refer_path - Check if a rename or link action is allowed
+ *
+ * @old_dentry: File or directory requested to be moved or linked.
+ * @new_dir: Destination parent directory.
+ * @new_dentry: Destination file or directory.
+ * @removable: Sets to true if it is a rename operation.
+ * @exchange: Sets to true if it is a rename operation with RENAME_EXCHANGE.
+ *
+ * Because of its unprivileged constraints, Landlock relies on file hierarchies
+ * (and not only inodes) to tie access rights to files.  Being able to link or
+ * rename a file hierarchy brings some challenges.  Indeed, moving or linking a
+ * file (i.e. creating a new reference to an inode) can have an impact on the
+ * actions allowed for a set of files if it would change its parent directory
+ * (i.e. reparenting).
+ *
+ * To avoid trivial access right bypasses, Landlock first checks if the file or
+ * directory requested to be moved would gain new access rights inherited from
+ * its new hierarchy.  Before returning any error, Landlock then checks that
+ * the parent source hierarchy and the destination hierarchy would allow the
+ * link or rename action.  If it is not the case, an error with EACCES is
+ * returned to inform user space that there is no way to remove or create the
+ * requested source file type.  If it should be allowed but the new inherited
+ * access rights would be greater than the source access rights, then the
+ * kernel returns an error with EXDEV.  Prioritizing EACCES over EXDEV enables
+ * user space to abort the whole operation if there is no way to do it, or to
+ * manually copy the source to the destination if this remains allowed, e.g.
+ * because file creation is allowed on the destination directory but not direct
+ * linking.
+ *
+ * To achieve this goal, the kernel needs to compare two file hierarchies: the
+ * one identifying the source file or directory (including itself), and the
+ * destination one.  This can be seen as a multilayer partial ordering problem.
+ * The kernel walks through these paths and collects in a matrix the access
+ * rights that are denied per layer.  These matrices are then compared to see
+ * if the destination one has more (or the same) restrictions as the source
+ * one.  If this is the case, the requested action will not return EXDEV, which
+ * doesn't mean the action is allowed.  The parent hierarchy of the source
+ * (i.e. parent directory), and the destination hierarchy must also be checked
+ * to verify that they explicitly allow such action (i.e.  referencing,
+ * creation and potentially removal rights).  The kernel implementation is then
+ * required to rely on potentially four matrices of access rights: one for the
+ * source file or directory (i.e. the child), a potentially other one for the
+ * other source/destination (in case of RENAME_EXCHANGE), one for the source
+ * parent hierarchy and a last one for the destination hierarchy.  These
+ * ephemeral matrices take some space on the stack, which limits the number of
+ * layers to a deemed reasonable number: 16.
+ *
+ * Returns:
+ * - 0 if access is allowed;
+ * - -EXDEV if @old_dentry would inherit new access rights from @new_dir;
+ * - -EACCES if file removal or creation is denied.
+ */
+static int current_check_refer_path(struct dentry *const old_dentry,
+				    const struct path *const new_dir,
+				    struct dentry *const new_dentry,
+				    const bool removable, const bool exchange)
+{
+	const struct landlock_ruleset *const dom =
+		landlock_get_current_domain();
+	bool allow_parent1, allow_parent2;
+	access_mask_t access_request_parent1, access_request_parent2;
+	struct path mnt_dir;
+	layer_mask_t layer_masks_parent1[LANDLOCK_NUM_ACCESS_FS],
+		layer_masks_parent2[LANDLOCK_NUM_ACCESS_FS];
+
+	if (!dom)
+		return 0;
+	if (WARN_ON_ONCE(dom->num_layers < 1))
+		return -EACCES;
+	if (unlikely(d_is_negative(old_dentry)))
+		return -ENOENT;
+	if (exchange) {
+		if (unlikely(d_is_negative(new_dentry)))
+			return -ENOENT;
+		access_request_parent1 =
+			get_mode_access(d_backing_inode(new_dentry)->i_mode);
+	} else {
+		access_request_parent1 = 0;
+	}
+	access_request_parent2 =
+		get_mode_access(d_backing_inode(old_dentry)->i_mode);
+	if (removable) {
+		access_request_parent1 |= maybe_remove(old_dentry);
+		access_request_parent2 |= maybe_remove(new_dentry);
+	}
+
+	/* The mount points are the same for old and new paths, cf. EXDEV. */
+	if (old_dentry->d_parent == new_dir->dentry) {
+		/*
+		 * The LANDLOCK_ACCESS_FS_REFER access right is not required
+		 * for same-directory referer (i.e. no reparenting).
+		 */
+		access_request_parent1 = init_layer_masks(
+			dom, access_request_parent1 | access_request_parent2,
+			&layer_masks_parent1);
+		if (is_access_to_paths_allowed(
+			    dom, new_dir, access_request_parent1,
+			    &layer_masks_parent1, NULL, 0, NULL, NULL))
+			return 0;
+		return -EACCES;
+	}
+
+	access_request_parent1 |= LANDLOCK_ACCESS_FS_REFER;
+	access_request_parent2 |= LANDLOCK_ACCESS_FS_REFER;
+
+	/* Saves the common mount point. */
+	mnt_dir.mnt = new_dir->mnt;
+	mnt_dir.dentry = new_dir->mnt->mnt_root;
+
+	/* new_dir->dentry is equal to new_dentry->d_parent */
+	allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry,
+						old_dentry->d_parent,
+						&layer_masks_parent1);
+	allow_parent2 = collect_domain_accesses(
+		dom, mnt_dir.dentry, new_dir->dentry, &layer_masks_parent2);
+
+	if (allow_parent1 && allow_parent2)
+		return 0;
+
+	/*
+	 * To be able to compare source and destination domain access rights,
+	 * take into account the @old_dentry access rights aggregated with its
+	 * parent access rights.  This will be useful to compare with the
+	 * destination parent access rights.
+	 */
+	if (is_access_to_paths_allowed(
+		    dom, &mnt_dir, access_request_parent1, &layer_masks_parent1,
+		    old_dentry, access_request_parent2, &layer_masks_parent2,
+		    exchange ? new_dentry : NULL))
+		return 0;
+
+	/*
+	 * This prioritizes EACCES over EXDEV for all actions, including
+	 * renames with RENAME_EXCHANGE.
+	 */
+	if (likely(is_eacces(&layer_masks_parent1, access_request_parent1) ||
+		   is_eacces(&layer_masks_parent2, access_request_parent2)))
+		return -EACCES;
+
+	/*
+	 * Gracefully forbids reparenting if the destination directory
+	 * hierarchy is not a superset of restrictions of the source directory
+	 * hierarchy, or if LANDLOCK_ACCESS_FS_REFER is not allowed by the
+	 * source or the destination.
+	 */
+	return -EXDEV;
+}
+
+/* Inode hooks */
+
+static void hook_inode_free_security(struct inode *const inode)
+{
+	/*
+	 * All inodes must already have been untied from their object by
+	 * release_inode() or hook_sb_delete().
+	 */
+	WARN_ON_ONCE(landlock_inode(inode)->object);
+}
+
+/* Super-block hooks */
+
+/*
+ * Release the inodes used in a security policy.
+ *
+ * Cf. fsnotify_unmount_inodes() and invalidate_inodes()
+ */
+static void hook_sb_delete(struct super_block *const sb)
+{
+	struct inode *inode, *prev_inode = NULL;
+
+	if (!landlock_initialized)
+		return;
+
+	spin_lock(&sb->s_inode_list_lock);
+	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+		struct landlock_object *object;
+
+		/* Only handles referenced inodes. */
+		if (!atomic_read(&inode->i_count))
+			continue;
+
+		/*
+		 * Protects against concurrent modification of inode (e.g.
+		 * from get_inode_object()).
+		 */
+		spin_lock(&inode->i_lock);
+		/*
+		 * Checks I_FREEING and I_WILL_FREE  to protect against a race
+		 * condition when release_inode() just called iput(), which
+		 * could lead to a NULL dereference of inode->security or a
+		 * second call to iput() for the same Landlock object.  Also
+		 * checks I_NEW because such inode cannot be tied to an object.
+		 */
+		if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) {
+			spin_unlock(&inode->i_lock);
+			continue;
+		}
+
+		rcu_read_lock();
+		object = rcu_dereference(landlock_inode(inode)->object);
+		if (!object) {
+			rcu_read_unlock();
+			spin_unlock(&inode->i_lock);
+			continue;
+		}
+		/* Keeps a reference to this inode until the next loop walk. */
+		__iget(inode);
+		spin_unlock(&inode->i_lock);
+
+		/*
+		 * If there is no concurrent release_inode() ongoing, then we
+		 * are in charge of calling iput() on this inode, otherwise we
+		 * will just wait for it to finish.
+		 */
+		spin_lock(&object->lock);
+		if (object->underobj == inode) {
+			object->underobj = NULL;
+			spin_unlock(&object->lock);
+			rcu_read_unlock();
+
+			/*
+			 * Because object->underobj was not NULL,
+			 * release_inode() and get_inode_object() guarantee
+			 * that it is safe to reset
+			 * landlock_inode(inode)->object while it is not NULL.
+			 * It is therefore not necessary to lock inode->i_lock.
+			 */
+			rcu_assign_pointer(landlock_inode(inode)->object, NULL);
+			/*
+			 * At this point, we own the ihold() reference that was
+			 * originally set up by get_inode_object() and the
+			 * __iget() reference that we just set in this loop
+			 * walk.  Therefore the following call to iput() will
+			 * not sleep nor drop the inode because there is now at
+			 * least two references to it.
+			 */
+			iput(inode);
+		} else {
+			spin_unlock(&object->lock);
+			rcu_read_unlock();
+		}
+
+		if (prev_inode) {
+			/*
+			 * At this point, we still own the __iget() reference
+			 * that we just set in this loop walk.  Therefore we
+			 * can drop the list lock and know that the inode won't
+			 * disappear from under us until the next loop walk.
+			 */
+			spin_unlock(&sb->s_inode_list_lock);
+			/*
+			 * We can now actually put the inode reference from the
+			 * previous loop walk, which is not needed anymore.
+			 */
+			iput(prev_inode);
+			cond_resched();
+			spin_lock(&sb->s_inode_list_lock);
+		}
+		prev_inode = inode;
+	}
+	spin_unlock(&sb->s_inode_list_lock);
+
+	/* Puts the inode reference from the last loop walk, if any. */
+	if (prev_inode)
+		iput(prev_inode);
+	/* Waits for pending iput() in release_inode(). */
+	wait_var_event(&landlock_superblock(sb)->inode_refs,
+		       !atomic_long_read(&landlock_superblock(sb)->inode_refs));
+}
+
+/*
+ * Because a Landlock security policy is defined according to the filesystem
+ * topology (i.e. the mount namespace), changing it may grant access to files
+ * not previously allowed.
+ *
+ * To make it simple, deny any filesystem topology modification by landlocked
+ * processes.  Non-landlocked processes may still change the namespace of a
+ * landlocked process, but this kind of threat must be handled by a system-wide
+ * access-control security policy.
+ *
+ * This could be lifted in the future if Landlock can safely handle mount
+ * namespace updates requested by a landlocked process.  Indeed, we could
+ * update the current domain (which is currently read-only) by taking into
+ * account the accesses of the source and the destination of a new mount point.
+ * However, it would also require to make all the child domains dynamically
+ * inherit these new constraints.  Anyway, for backward compatibility reasons,
+ * a dedicated user space option would be required (e.g. as a ruleset flag).
+ */
+static int hook_sb_mount(const char *const dev_name,
+			 const struct path *const path, const char *const type,
+			 const unsigned long flags, void *const data)
+{
+	if (!landlock_get_current_domain())
+		return 0;
+	return -EPERM;
+}
+
+static int hook_move_mount(const struct path *const from_path,
+			   const struct path *const to_path)
+{
+	if (!landlock_get_current_domain())
+		return 0;
+	return -EPERM;
+}
+
+/*
+ * Removing a mount point may reveal a previously hidden file hierarchy, which
+ * may then grant access to files, which may have previously been forbidden.
+ */
+static int hook_sb_umount(struct vfsmount *const mnt, const int flags)
+{
+	if (!landlock_get_current_domain())
+		return 0;
+	return -EPERM;
+}
+
+static int hook_sb_remount(struct super_block *const sb, void *const mnt_opts)
+{
+	if (!landlock_get_current_domain())
+		return 0;
+	return -EPERM;
+}
+
+/*
+ * pivot_root(2), like mount(2), changes the current mount namespace.  It must
+ * then be forbidden for a landlocked process.
+ *
+ * However, chroot(2) may be allowed because it only changes the relative root
+ * directory of the current process.  Moreover, it can be used to restrict the
+ * view of the filesystem.
+ */
+static int hook_sb_pivotroot(const struct path *const old_path,
+			     const struct path *const new_path)
+{
+	if (!landlock_get_current_domain())
+		return 0;
+	return -EPERM;
+}
+
+/* Path hooks */
+
+static int hook_path_link(struct dentry *const old_dentry,
+			  const struct path *const new_dir,
+			  struct dentry *const new_dentry)
+{
+	return current_check_refer_path(old_dentry, new_dir, new_dentry, false,
+					false);
+}
+
+static int hook_path_rename(const struct path *const old_dir,
+			    struct dentry *const old_dentry,
+			    const struct path *const new_dir,
+			    struct dentry *const new_dentry,
+			    const unsigned int flags)
+{
+	/* old_dir refers to old_dentry->d_parent and new_dir->mnt */
+	return current_check_refer_path(old_dentry, new_dir, new_dentry, true,
+					!!(flags & RENAME_EXCHANGE));
+}
+
+static int hook_path_mkdir(const struct path *const dir,
+			   struct dentry *const dentry, const umode_t mode)
+{
+	return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_DIR);
+}
+
+static int hook_path_mknod(const struct path *const dir,
+			   struct dentry *const dentry, const umode_t mode,
+			   const unsigned int dev)
+{
+	const struct landlock_ruleset *const dom =
+		landlock_get_current_domain();
+
+	if (!dom)
+		return 0;
+	return check_access_path(dom, dir, get_mode_access(mode));
+}
+
+static int hook_path_symlink(const struct path *const dir,
+			     struct dentry *const dentry,
+			     const char *const old_name)
+{
+	return current_check_access_path(dir, LANDLOCK_ACCESS_FS_MAKE_SYM);
+}
+
+static int hook_path_unlink(const struct path *const dir,
+			    struct dentry *const dentry)
+{
+	return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_FILE);
+}
+
+static int hook_path_rmdir(const struct path *const dir,
+			   struct dentry *const dentry)
+{
+	return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_DIR);
+}
+
+static int hook_path_truncate(const struct path *const path)
+{
+	return current_check_access_path(path, LANDLOCK_ACCESS_FS_TRUNCATE);
+}
+
+/* File hooks */
+
+/**
+ * get_required_file_open_access - Get access needed to open a file
+ *
+ * @file: File being opened.
+ *
+ * Returns the access rights that are required for opening the given file,
+ * depending on the file type and open mode.
+ */
+static inline access_mask_t
+get_required_file_open_access(const struct file *const file)
+{
+	access_mask_t access = 0;
+
+	if (file->f_mode & FMODE_READ) {
+		/* A directory can only be opened in read mode. */
+		if (S_ISDIR(file_inode(file)->i_mode))
+			return LANDLOCK_ACCESS_FS_READ_DIR;
+		access = LANDLOCK_ACCESS_FS_READ_FILE;
+	}
+	if (file->f_mode & FMODE_WRITE)
+		access |= LANDLOCK_ACCESS_FS_WRITE_FILE;
+	/* __FMODE_EXEC is indeed part of f_flags, not f_mode. */
+	if (file->f_flags & __FMODE_EXEC)
+		access |= LANDLOCK_ACCESS_FS_EXECUTE;
+	return access;
+}
+
+static int hook_file_alloc_security(struct file *const file)
+{
+	/*
+	 * Grants all access rights, even if most of them are not checked later
+	 * on. It is more consistent.
+	 *
+	 * Notably, file descriptors for regular files can also be acquired
+	 * without going through the file_open hook, for example when using
+	 * memfd_create(2).
+	 */
+	landlock_file(file)->allowed_access = LANDLOCK_MASK_ACCESS_FS;
+	return 0;
+}
+
+static int hook_file_open(struct file *const file)
+{
+	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
+	access_mask_t open_access_request, full_access_request, allowed_access;
+	const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE;
+	const struct landlock_ruleset *const dom =
+		landlock_get_current_domain();
+
+	if (!dom)
+		return 0;
+
+	/*
+	 * Because a file may be opened with O_PATH, get_required_file_open_access()
+	 * may return 0.  This case will be handled with a future Landlock
+	 * evolution.
+	 */
+	open_access_request = get_required_file_open_access(file);
+
+	/*
+	 * We look up more access than what we immediately need for open(), so
+	 * that we can later authorize operations on opened files.
+	 */
+	full_access_request = open_access_request | optional_access;
+
+	if (is_access_to_paths_allowed(
+		    dom, &file->f_path,
+		    init_layer_masks(dom, full_access_request, &layer_masks),
+		    &layer_masks, NULL, 0, NULL, NULL)) {
+		allowed_access = full_access_request;
+	} else {
+		unsigned long access_bit;
+		const unsigned long access_req = full_access_request;
+
+		/*
+		 * Calculate the actual allowed access rights from layer_masks.
+		 * Add each access right to allowed_access which has not been
+		 * vetoed by any layer.
+		 */
+		allowed_access = 0;
+		for_each_set_bit(access_bit, &access_req,
+				 ARRAY_SIZE(layer_masks)) {
+			if (!layer_masks[access_bit])
+				allowed_access |= BIT_ULL(access_bit);
+		}
+	}
+
+	/*
+	 * For operations on already opened files (i.e. ftruncate()), it is the
+	 * access rights at the time of open() which decide whether the
+	 * operation is permitted. Therefore, we record the relevant subset of
+	 * file access rights in the opened struct file.
+	 */
+	landlock_file(file)->allowed_access = allowed_access;
+
+	if ((open_access_request & allowed_access) == open_access_request)
+		return 0;
+
+	return -EACCES;
+}
+
+static int hook_file_truncate(struct file *const file)
+{
+	/*
+	 * Allows truncation if the truncate right was available at the time of
+	 * opening the file, to get a consistent access check as for read, write
+	 * and execute operations.
+	 *
+	 * Note: For checks done based on the file's Landlock allowed access, we
+	 * enforce them independently of whether the current thread is in a
+	 * Landlock domain, so that open files passed between independent
+	 * processes retain their behaviour.
+	 */
+	if (landlock_file(file)->allowed_access & LANDLOCK_ACCESS_FS_TRUNCATE)
+		return 0;
+	return -EACCES;
+}
+
+static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
+	LSM_HOOK_INIT(inode_free_security, hook_inode_free_security),
+
+	LSM_HOOK_INIT(sb_delete, hook_sb_delete),
+	LSM_HOOK_INIT(sb_mount, hook_sb_mount),
+	LSM_HOOK_INIT(move_mount, hook_move_mount),
+	LSM_HOOK_INIT(sb_umount, hook_sb_umount),
+	LSM_HOOK_INIT(sb_remount, hook_sb_remount),
+	LSM_HOOK_INIT(sb_pivotroot, hook_sb_pivotroot),
+
+	LSM_HOOK_INIT(path_link, hook_path_link),
+	LSM_HOOK_INIT(path_rename, hook_path_rename),
+	LSM_HOOK_INIT(path_mkdir, hook_path_mkdir),
+	LSM_HOOK_INIT(path_mknod, hook_path_mknod),
+	LSM_HOOK_INIT(path_symlink, hook_path_symlink),
+	LSM_HOOK_INIT(path_unlink, hook_path_unlink),
+	LSM_HOOK_INIT(path_rmdir, hook_path_rmdir),
+	LSM_HOOK_INIT(path_truncate, hook_path_truncate),
+
+	LSM_HOOK_INIT(file_alloc_security, hook_file_alloc_security),
+	LSM_HOOK_INIT(file_open, hook_file_open),
+	LSM_HOOK_INIT(file_truncate, hook_file_truncate),
+};
+
+__init void landlock_add_fs_hooks(void)
+{
+	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
+			   LANDLOCK_NAME);
+}