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, 456 insertions, 0 deletions

diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
new file mode 100644
index 000000000..245cc650a
--- /dev/null
+++ b/security/landlock/syscalls.c
@@ -0,0 +1,456 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - System call implementations and user space interfaces
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ */
+
+#include <asm/current.h>
+#include <linux/anon_inodes.h>
+#include <linux/build_bug.h>
+#include <linux/capability.h>
+#include <linux/compiler_types.h>
+#include <linux/dcache.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/limits.h>
+#include <linux/mount.h>
+#include <linux/path.h>
+#include <linux/sched.h>
+#include <linux/security.h>
+#include <linux/stddef.h>
+#include <linux/syscalls.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+#include <uapi/linux/landlock.h>
+
+#include "cred.h"
+#include "fs.h"
+#include "limits.h"
+#include "ruleset.h"
+#include "setup.h"
+
+/**
+ * copy_min_struct_from_user - Safe future-proof argument copying
+ *
+ * Extend copy_struct_from_user() to check for consistent user buffer.
+ *
+ * @dst: Kernel space pointer or NULL.
+ * @ksize: Actual size of the data pointed to by @dst.
+ * @ksize_min: Minimal required size to be copied.
+ * @src: User space pointer or NULL.
+ * @usize: (Alleged) size of the data pointed to by @src.
+ */
+static __always_inline int
+copy_min_struct_from_user(void *const dst, const size_t ksize,
+			  const size_t ksize_min, const void __user *const src,
+			  const size_t usize)
+{
+	/* Checks buffer inconsistencies. */
+	BUILD_BUG_ON(!dst);
+	if (!src)
+		return -EFAULT;
+
+	/* Checks size ranges. */
+	BUILD_BUG_ON(ksize <= 0);
+	BUILD_BUG_ON(ksize < ksize_min);
+	if (usize < ksize_min)
+		return -EINVAL;
+	if (usize > PAGE_SIZE)
+		return -E2BIG;
+
+	/* Copies user buffer and fills with zeros. */
+	return copy_struct_from_user(dst, ksize, src, usize);
+}
+
+/*
+ * This function only contains arithmetic operations with constants, leading to
+ * BUILD_BUG_ON().  The related code is evaluated and checked at build time,
+ * but it is then ignored thanks to compiler optimizations.
+ */
+static void build_check_abi(void)
+{
+	struct landlock_ruleset_attr ruleset_attr;
+	struct landlock_path_beneath_attr path_beneath_attr;
+	size_t ruleset_size, path_beneath_size;
+
+	/*
+	 * For each user space ABI structures, first checks that there is no
+	 * hole in them, then checks that all architectures have the same
+	 * struct size.
+	 */
+	ruleset_size = sizeof(ruleset_attr.handled_access_fs);
+	BUILD_BUG_ON(sizeof(ruleset_attr) != ruleset_size);
+	BUILD_BUG_ON(sizeof(ruleset_attr) != 8);
+
+	path_beneath_size = sizeof(path_beneath_attr.allowed_access);
+	path_beneath_size += sizeof(path_beneath_attr.parent_fd);
+	BUILD_BUG_ON(sizeof(path_beneath_attr) != path_beneath_size);
+	BUILD_BUG_ON(sizeof(path_beneath_attr) != 12);
+}
+
+/* Ruleset handling */
+
+static int fop_ruleset_release(struct inode *const inode,
+			       struct file *const filp)
+{
+	struct landlock_ruleset *ruleset = filp->private_data;
+
+	landlock_put_ruleset(ruleset);
+	return 0;
+}
+
+static ssize_t fop_dummy_read(struct file *const filp, char __user *const buf,
+			      const size_t size, loff_t *const ppos)
+{
+	/* Dummy handler to enable FMODE_CAN_READ. */
+	return -EINVAL;
+}
+
+static ssize_t fop_dummy_write(struct file *const filp,
+			       const char __user *const buf, const size_t size,
+			       loff_t *const ppos)
+{
+	/* Dummy handler to enable FMODE_CAN_WRITE. */
+	return -EINVAL;
+}
+
+/*
+ * A ruleset file descriptor enables to build a ruleset by adding (i.e.
+ * writing) rule after rule, without relying on the task's context.  This
+ * reentrant design is also used in a read way to enforce the ruleset on the
+ * current task.
+ */
+static const struct file_operations ruleset_fops = {
+	.release = fop_ruleset_release,
+	.read = fop_dummy_read,
+	.write = fop_dummy_write,
+};
+
+#define LANDLOCK_ABI_VERSION 3
+
+/**
+ * sys_landlock_create_ruleset - Create a new ruleset
+ *
+ * @attr: Pointer to a &struct landlock_ruleset_attr identifying the scope of
+ *        the new ruleset.
+ * @size: Size of the pointed &struct landlock_ruleset_attr (needed for
+ *        backward and forward compatibility).
+ * @flags: Supported value: %LANDLOCK_CREATE_RULESET_VERSION.
+ *
+ * This system call enables to create a new Landlock ruleset, and returns the
+ * related file descriptor on success.
+ *
+ * If @flags is %LANDLOCK_CREATE_RULESET_VERSION and @attr is NULL and @size is
+ * 0, then the returned value is the highest supported Landlock ABI version
+ * (starting at 1).
+ *
+ * Possible returned errors are:
+ *
+ * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
+ * - %EINVAL: unknown @flags, or unknown access, or too small @size;
+ * - %E2BIG or %EFAULT: @attr or @size inconsistencies;
+ * - %ENOMSG: empty &landlock_ruleset_attr.handled_access_fs.
+ */
+SYSCALL_DEFINE3(landlock_create_ruleset,
+		const struct landlock_ruleset_attr __user *const, attr,
+		const size_t, size, const __u32, flags)
+{
+	struct landlock_ruleset_attr ruleset_attr;
+	struct landlock_ruleset *ruleset;
+	int err, ruleset_fd;
+
+	/* Build-time checks. */
+	build_check_abi();
+
+	if (!landlock_initialized)
+		return -EOPNOTSUPP;
+
+	if (flags) {
+		if ((flags == LANDLOCK_CREATE_RULESET_VERSION) && !attr &&
+		    !size)
+			return LANDLOCK_ABI_VERSION;
+		return -EINVAL;
+	}
+
+	/* Copies raw user space buffer. */
+	err = copy_min_struct_from_user(&ruleset_attr, sizeof(ruleset_attr),
+					offsetofend(typeof(ruleset_attr),
+						    handled_access_fs),
+					attr, size);
+	if (err)
+		return err;
+
+	/* Checks content (and 32-bits cast). */
+	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_ACCESS_FS) !=
+	    LANDLOCK_MASK_ACCESS_FS)
+		return -EINVAL;
+
+	/* Checks arguments and transforms to kernel struct. */
+	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs);
+	if (IS_ERR(ruleset))
+		return PTR_ERR(ruleset);
+
+	/* Creates anonymous FD referring to the ruleset. */
+	ruleset_fd = anon_inode_getfd("[landlock-ruleset]", &ruleset_fops,
+				      ruleset, O_RDWR | O_CLOEXEC);
+	if (ruleset_fd < 0)
+		landlock_put_ruleset(ruleset);
+	return ruleset_fd;
+}
+
+/*
+ * Returns an owned ruleset from a FD. It is thus needed to call
+ * landlock_put_ruleset() on the return value.
+ */
+static struct landlock_ruleset *get_ruleset_from_fd(const int fd,
+						    const fmode_t mode)
+{
+	struct fd ruleset_f;
+	struct landlock_ruleset *ruleset;
+
+	ruleset_f = fdget(fd);
+	if (!ruleset_f.file)
+		return ERR_PTR(-EBADF);
+
+	/* Checks FD type and access right. */
+	if (ruleset_f.file->f_op != &ruleset_fops) {
+		ruleset = ERR_PTR(-EBADFD);
+		goto out_fdput;
+	}
+	if (!(ruleset_f.file->f_mode & mode)) {
+		ruleset = ERR_PTR(-EPERM);
+		goto out_fdput;
+	}
+	ruleset = ruleset_f.file->private_data;
+	if (WARN_ON_ONCE(ruleset->num_layers != 1)) {
+		ruleset = ERR_PTR(-EINVAL);
+		goto out_fdput;
+	}
+	landlock_get_ruleset(ruleset);
+
+out_fdput:
+	fdput(ruleset_f);
+	return ruleset;
+}
+
+/* Path handling */
+
+/*
+ * @path: Must call put_path(@path) after the call if it succeeded.
+ */
+static int get_path_from_fd(const s32 fd, struct path *const path)
+{
+	struct fd f;
+	int err = 0;
+
+	BUILD_BUG_ON(!__same_type(
+		fd, ((struct landlock_path_beneath_attr *)NULL)->parent_fd));
+
+	/* Handles O_PATH. */
+	f = fdget_raw(fd);
+	if (!f.file)
+		return -EBADF;
+	/*
+	 * Forbids ruleset FDs, internal filesystems (e.g. nsfs), including
+	 * pseudo filesystems that will never be mountable (e.g. sockfs,
+	 * pipefs).
+	 */
+	if ((f.file->f_op == &ruleset_fops) ||
+	    (f.file->f_path.mnt->mnt_flags & MNT_INTERNAL) ||
+	    (f.file->f_path.dentry->d_sb->s_flags & SB_NOUSER) ||
+	    d_is_negative(f.file->f_path.dentry) ||
+	    IS_PRIVATE(d_backing_inode(f.file->f_path.dentry))) {
+		err = -EBADFD;
+		goto out_fdput;
+	}
+	*path = f.file->f_path;
+	path_get(path);
+
+out_fdput:
+	fdput(f);
+	return err;
+}
+
+/**
+ * sys_landlock_add_rule - Add a new rule to a ruleset
+ *
+ * @ruleset_fd: File descriptor tied to the ruleset that should be extended
+ *		with the new rule.
+ * @rule_type: Identify the structure type pointed to by @rule_attr (only
+ *             %LANDLOCK_RULE_PATH_BENEATH for now).
+ * @rule_attr: Pointer to a rule (only of type &struct
+ *             landlock_path_beneath_attr for now).
+ * @flags: Must be 0.
+ *
+ * This system call enables to define a new rule and add it to an existing
+ * ruleset.
+ *
+ * Possible returned errors are:
+ *
+ * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
+ * - %EINVAL: @flags is not 0, or inconsistent access in the rule (i.e.
+ *   &landlock_path_beneath_attr.allowed_access is not a subset of the
+ *   ruleset handled accesses);
+ * - %ENOMSG: Empty accesses (e.g. &landlock_path_beneath_attr.allowed_access);
+ * - %EBADF: @ruleset_fd is not a file descriptor for the current thread, or a
+ *   member of @rule_attr is not a file descriptor as expected;
+ * - %EBADFD: @ruleset_fd is not a ruleset file descriptor, or a member of
+ *   @rule_attr is not the expected file descriptor type;
+ * - %EPERM: @ruleset_fd has no write access to the underlying ruleset;
+ * - %EFAULT: @rule_attr inconsistency.
+ */
+SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
+		const enum landlock_rule_type, rule_type,
+		const void __user *const, rule_attr, const __u32, flags)
+{
+	struct landlock_path_beneath_attr path_beneath_attr;
+	struct path path;
+	struct landlock_ruleset *ruleset;
+	int res, err;
+
+	if (!landlock_initialized)
+		return -EOPNOTSUPP;
+
+	/* No flag for now. */
+	if (flags)
+		return -EINVAL;
+
+	/* Gets and checks the ruleset. */
+	ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_WRITE);
+	if (IS_ERR(ruleset))
+		return PTR_ERR(ruleset);
+
+	if (rule_type != LANDLOCK_RULE_PATH_BENEATH) {
+		err = -EINVAL;
+		goto out_put_ruleset;
+	}
+
+	/* Copies raw user space buffer, only one type for now. */
+	res = copy_from_user(&path_beneath_attr, rule_attr,
+			     sizeof(path_beneath_attr));
+	if (res) {
+		err = -EFAULT;
+		goto out_put_ruleset;
+	}
+
+	/*
+	 * Informs about useless rule: empty allowed_access (i.e. deny rules)
+	 * are ignored in path walks.
+	 */
+	if (!path_beneath_attr.allowed_access) {
+		err = -ENOMSG;
+		goto out_put_ruleset;
+	}
+	/*
+	 * Checks that allowed_access matches the @ruleset constraints
+	 * (ruleset->fs_access_masks[0] is automatically upgraded to 64-bits).
+	 */
+	if ((path_beneath_attr.allowed_access | ruleset->fs_access_masks[0]) !=
+	    ruleset->fs_access_masks[0]) {
+		err = -EINVAL;
+		goto out_put_ruleset;
+	}
+
+	/* Gets and checks the new rule. */
+	err = get_path_from_fd(path_beneath_attr.parent_fd, &path);
+	if (err)
+		goto out_put_ruleset;
+
+	/* Imports the new rule. */
+	err = landlock_append_fs_rule(ruleset, &path,
+				      path_beneath_attr.allowed_access);
+	path_put(&path);
+
+out_put_ruleset:
+	landlock_put_ruleset(ruleset);
+	return err;
+}
+
+/* Enforcement */
+
+/**
+ * sys_landlock_restrict_self - Enforce a ruleset on the calling thread
+ *
+ * @ruleset_fd: File descriptor tied to the ruleset to merge with the target.
+ * @flags: Must be 0.
+ *
+ * This system call enables to enforce a Landlock ruleset on the current
+ * thread.  Enforcing a ruleset requires that the task has %CAP_SYS_ADMIN in its
+ * namespace or is running with no_new_privs.  This avoids scenarios where
+ * unprivileged tasks can affect the behavior of privileged children.
+ *
+ * Possible returned errors are:
+ *
+ * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
+ * - %EINVAL: @flags is not 0.
+ * - %EBADF: @ruleset_fd is not a file descriptor for the current thread;
+ * - %EBADFD: @ruleset_fd is not a ruleset file descriptor;
+ * - %EPERM: @ruleset_fd has no read access to the underlying ruleset, or the
+ *   current thread is not running with no_new_privs, or it doesn't have
+ *   %CAP_SYS_ADMIN in its namespace.
+ * - %E2BIG: The maximum number of stacked rulesets is reached for the current
+ *   thread.
+ */
+SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
+		flags)
+{
+	struct landlock_ruleset *new_dom, *ruleset;
+	struct cred *new_cred;
+	struct landlock_cred_security *new_llcred;
+	int err;
+
+	if (!landlock_initialized)
+		return -EOPNOTSUPP;
+
+	/*
+	 * Similar checks as for seccomp(2), except that an -EPERM may be
+	 * returned.
+	 */
+	if (!task_no_new_privs(current) &&
+	    !ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
+		return -EPERM;
+
+	/* No flag for now. */
+	if (flags)
+		return -EINVAL;
+
+	/* Gets and checks the ruleset. */
+	ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_READ);
+	if (IS_ERR(ruleset))
+		return PTR_ERR(ruleset);
+
+	/* Prepares new credentials. */
+	new_cred = prepare_creds();
+	if (!new_cred) {
+		err = -ENOMEM;
+		goto out_put_ruleset;
+	}
+	new_llcred = landlock_cred(new_cred);
+
+	/*
+	 * There is no possible race condition while copying and manipulating
+	 * the current credentials because they are dedicated per thread.
+	 */
+	new_dom = landlock_merge_ruleset(new_llcred->domain, ruleset);
+	if (IS_ERR(new_dom)) {
+		err = PTR_ERR(new_dom);
+		goto out_put_creds;
+	}
+
+	/* Replaces the old (prepared) domain. */
+	landlock_put_ruleset(new_llcred->domain);
+	new_llcred->domain = new_dom;
+
+	landlock_put_ruleset(ruleset);
+	return commit_creds(new_cred);
+
+out_put_creds:
+	abort_creds(new_cred);
+
+out_put_ruleset:
+	landlock_put_ruleset(ruleset);
+	return err;
+}