diff --git a/MAINTAINERS b/MAINTAINERS
index a5689e2c1aa51ccfd04bc8f8344d9a8d5ca62db4..3e833d20d0f5a5879ec3ad105dbdf1f940984529 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12861,6 +12861,7 @@ S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git
 F:	samples/pidfd/
 F:	tools/testing/selftests/pidfd/
+F:	tools/testing/selftests/clone3/
 K:	(?i)pidfd
 K:	(?i)clone3
 K:	\b(clone_args|kernel_clone_args)\b
diff --git a/include/linux/pid.h b/include/linux/pid.h
index 9645b1194c9812adc23c62b9518c305c3dcacf40..998ae7d2445092aefc4d88f20c4e37db8380c5b2 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -85,6 +85,10 @@ static inline struct pid *get_pid(struct pid *pid)
 
 extern void put_pid(struct pid *pid);
 extern struct task_struct *pid_task(struct pid *pid, enum pid_type);
+static inline bool pid_has_task(struct pid *pid, enum pid_type type)
+{
+	return !hlist_empty(&pid->tasks[type]);
+}
 extern struct task_struct *get_pid_task(struct pid *pid, enum pid_type);
 
 extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type);
@@ -120,7 +124,8 @@ extern struct pid *find_vpid(int nr);
 extern struct pid *find_get_pid(int nr);
 extern struct pid *find_ge_pid(int nr, struct pid_namespace *);
 
-extern struct pid *alloc_pid(struct pid_namespace *ns);
+extern struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
+			     size_t set_tid_size);
 extern void free_pid(struct pid *pid);
 extern void disable_pid_allocation(struct pid_namespace *ns);
 
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 49538b172483c4f519100e1617f42d0f897bfbaa..2ed6af88794b0bf9adffdcf861cf9f0358305630 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -12,6 +12,8 @@
 #include <linux/ns_common.h>
 #include <linux/idr.h>
 
+/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
+#define MAX_PID_NS_LEVEL 32
 
 struct fs_pin;
 
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 4b1c3b664f517e5e35e6f581282e432649f734d7..f1879884238e95690e6010f81cac1a158ddb8af0 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -26,6 +26,9 @@ struct kernel_clone_args {
 	unsigned long stack;
 	unsigned long stack_size;
 	unsigned long tls;
+	pid_t *set_tid;
+	/* Number of elements in *set_tid */
+	size_t set_tid_size;
 };
 
 /*
diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
index 25b4fa00bad1f4ccc22f7dfe708a95807415b151..4a02178324641f555336164316ba2e30805c3719 100644
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -33,31 +33,48 @@
 #define CLONE_NEWNET		0x40000000	/* New network namespace */
 #define CLONE_IO		0x80000000	/* Clone io context */
 
+/* Flags for the clone3() syscall. */
+#define CLONE_CLEAR_SIGHAND 0x100000000ULL /* Clear any signal handler and reset to SIG_DFL. */
+
 #ifndef __ASSEMBLY__
 /**
  * struct clone_args - arguments for the clone3 syscall
- * @flags:       Flags for the new process as listed above.
- *               All flags are valid except for CSIGNAL and
- *               CLONE_DETACHED.
- * @pidfd:       If CLONE_PIDFD is set, a pidfd will be
- *               returned in this argument.
- * @child_tid:   If CLONE_CHILD_SETTID is set, the TID of the
- *               child process will be returned in the child's
- *               memory.
- * @parent_tid:  If CLONE_PARENT_SETTID is set, the TID of
- *               the child process will be returned in the
- *               parent's memory.
- * @exit_signal: The exit_signal the parent process will be
- *               sent when the child exits.
- * @stack:       Specify the location of the stack for the
- *               child process.
- *               Note, @stack is expected to point to the
- *               lowest address. The stack direction will be
- *               determined by the kernel and set up
- *               appropriately based on @stack_size.
- * @stack_size:  The size of the stack for the child process.
- * @tls:         If CLONE_SETTLS is set, the tls descriptor
- *               is set to tls.
+ * @flags:        Flags for the new process as listed above.
+ *                All flags are valid except for CSIGNAL and
+ *                CLONE_DETACHED.
+ * @pidfd:        If CLONE_PIDFD is set, a pidfd will be
+ *                returned in this argument.
+ * @child_tid:    If CLONE_CHILD_SETTID is set, the TID of the
+ *                child process will be returned in the child's
+ *                memory.
+ * @parent_tid:   If CLONE_PARENT_SETTID is set, the TID of
+ *                the child process will be returned in the
+ *                parent's memory.
+ * @exit_signal:  The exit_signal the parent process will be
+ *                sent when the child exits.
+ * @stack:        Specify the location of the stack for the
+ *                child process.
+ *                Note, @stack is expected to point to the
+ *                lowest address. The stack direction will be
+ *                determined by the kernel and set up
+ *                appropriately based on @stack_size.
+ * @stack_size:   The size of the stack for the child process.
+ * @tls:          If CLONE_SETTLS is set, the tls descriptor
+ *                is set to tls.
+ * @set_tid:      Pointer to an array of type *pid_t. The size
+ *                of the array is defined using @set_tid_size.
+ *                This array is used to select PIDs/TIDs for
+ *                newly created processes. The first element in
+ *                this defines the PID in the most nested PID
+ *                namespace. Each additional element in the array
+ *                defines the PID in the parent PID namespace of
+ *                the original PID namespace. If the array has
+ *                less entries than the number of currently
+ *                nested PID namespaces only the PIDs in the
+ *                corresponding namespaces are set.
+ * @set_tid_size: This defines the size of the array referenced
+ *                in @set_tid. This cannot be larger than the
+ *                kernel's limit of nested PID namespaces.
  *
  * The structure is versioned by size and thus extensible.
  * New struct members must go at the end of the struct and
@@ -72,10 +89,13 @@ struct clone_args {
 	__aligned_u64 stack;
 	__aligned_u64 stack_size;
 	__aligned_u64 tls;
+	__aligned_u64 set_tid;
+	__aligned_u64 set_tid_size;
 };
 #endif
 
 #define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
+#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */
 
 /*
  * Scheduling policies
diff --git a/kernel/exit.c b/kernel/exit.c
index a46a50d67002d9877b00c8052ba922e02e9740af..f2d20ab7442276be9663e8c05c2a33c25de88f04 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1457,7 +1457,7 @@ static long do_wait(struct wait_opts *wo)
 	 */
 	wo->notask_error = -ECHILD;
 	if ((wo->wo_type < PIDTYPE_MAX) &&
-	   (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
+	   (!wo->wo_pid || !pid_has_task(wo->wo_pid, wo->wo_type)))
 		goto notask;
 
 	set_current_state(TASK_INTERRUPTIBLE);
diff --git a/kernel/fork.c b/kernel/fork.c
index 13b38794efb56940c18592d0ef26904d5cacb100..35f91ee9105772d7653ef21cd5f7af2bcd060fb1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1517,6 +1517,11 @@ static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 	spin_lock_irq(&current->sighand->siglock);
 	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 	spin_unlock_irq(&current->sighand->siglock);
+
+	/* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
+	if (clone_flags & CLONE_CLEAR_SIGHAND)
+		flush_signal_handlers(tsk, 0);
+
 	return 0;
 }
 
@@ -1695,12 +1700,68 @@ static int pidfd_release(struct inode *inode, struct file *file)
 }
 
 #ifdef CONFIG_PROC_FS
+/**
+ * pidfd_show_fdinfo - print information about a pidfd
+ * @m: proc fdinfo file
+ * @f: file referencing a pidfd
+ *
+ * Pid:
+ * This function will print the pid that a given pidfd refers to in the
+ * pid namespace of the procfs instance.
+ * If the pid namespace of the process is not a descendant of the pid
+ * namespace of the procfs instance 0 will be shown as its pid. This is
+ * similar to calling getppid() on a process whose parent is outside of
+ * its pid namespace.
+ *
+ * NSpid:
+ * If pid namespaces are supported then this function will also print
+ * the pid of a given pidfd refers to for all descendant pid namespaces
+ * starting from the current pid namespace of the instance, i.e. the
+ * Pid field and the first entry in the NSpid field will be identical.
+ * If the pid namespace of the process is not a descendant of the pid
+ * namespace of the procfs instance 0 will be shown as its first NSpid
+ * entry and no others will be shown.
+ * Note that this differs from the Pid and NSpid fields in
+ * /proc/<pid>/status where Pid and NSpid are always shown relative to
+ * the  pid namespace of the procfs instance. The difference becomes
+ * obvious when sending around a pidfd between pid namespaces from a
+ * different branch of the tree, i.e. where no ancestoral relation is
+ * present between the pid namespaces:
+ * - create two new pid namespaces ns1 and ns2 in the initial pid
+ *   namespace (also take care to create new mount namespaces in the
+ *   new pid namespace and mount procfs)
+ * - create a process with a pidfd in ns1
+ * - send pidfd from ns1 to ns2
+ * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
+ *   have exactly one entry, which is 0
+ */
 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
 {
-	struct pid_namespace *ns = proc_pid_ns(file_inode(m->file));
 	struct pid *pid = f->private_data;
+	struct pid_namespace *ns;
+	pid_t nr = -1;
+
+	if (likely(pid_has_task(pid, PIDTYPE_PID))) {
+		ns = proc_pid_ns(file_inode(m->file));
+		nr = pid_nr_ns(pid, ns);
+	}
+
+	seq_put_decimal_ll(m, "Pid:\t", nr);
+
+#ifdef CONFIG_PID_NS
+	seq_put_decimal_ll(m, "\nNSpid:\t", nr);
+	if (nr > 0) {
+		int i;
 
-	seq_put_decimal_ull(m, "Pid:\t", pid_nr_ns(pid, ns));
+		/* If nr is non-zero it means that 'pid' is valid and that
+		 * ns, i.e. the pid namespace associated with the procfs
+		 * instance, is in the pid namespace hierarchy of pid.
+		 * Start at one below the already printed level.
+		 */
+		for (i = ns->level + 1; i <= pid->level; i++)
+			seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
+	}
+#endif
 	seq_putc(m, '\n');
 }
 #endif
@@ -2026,7 +2087,8 @@ static __latent_entropy struct task_struct *copy_process(
 	stackleak_task_init(p);
 
 	if (pid != &init_struct_pid) {
-		pid = alloc_pid(p->nsproxy->pid_ns_for_children);
+		pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
+				args->set_tid_size);
 		if (IS_ERR(pid)) {
 			retval = PTR_ERR(pid);
 			goto bad_fork_cleanup_thread;
@@ -2529,6 +2591,7 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
 {
 	int err;
 	struct clone_args args;
+	pid_t *kset_tid = kargs->set_tid;
 
 	if (unlikely(usize > PAGE_SIZE))
 		return -E2BIG;
@@ -2539,6 +2602,15 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
 	if (err)
 		return err;
 
+	if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
+		return -EINVAL;
+
+	if (unlikely(!args.set_tid && args.set_tid_size > 0))
+		return -EINVAL;
+
+	if (unlikely(args.set_tid && args.set_tid_size == 0))
+		return -EINVAL;
+
 	/*
 	 * Verify that higher 32bits of exit_signal are unset and that
 	 * it is a valid signal
@@ -2556,8 +2628,16 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
 		.stack		= args.stack,
 		.stack_size	= args.stack_size,
 		.tls		= args.tls,
+		.set_tid_size	= args.set_tid_size,
 	};
 
+	if (args.set_tid &&
+		copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
+			(kargs->set_tid_size * sizeof(pid_t))))
+		return -EFAULT;
+
+	kargs->set_tid = kset_tid;
+
 	return 0;
 }
 
@@ -2591,11 +2671,8 @@ static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
 
 static bool clone3_args_valid(struct kernel_clone_args *kargs)
 {
-	/*
-	 * All lower bits of the flag word are taken.
-	 * Verify that no other unknown flags are passed along.
-	 */
-	if (kargs->flags & ~CLONE_LEGACY_FLAGS)
+	/* Verify that no unknown flags are passed along. */
+	if (kargs->flags & ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND))
 		return false;
 
 	/*
@@ -2605,6 +2682,10 @@ static bool clone3_args_valid(struct kernel_clone_args *kargs)
 	if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
 		return false;
 
+	if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
+	    (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
+		return false;
+
 	if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
 	    kargs->exit_signal)
 		return false;
@@ -2631,6 +2712,9 @@ SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
 	int err;
 
 	struct kernel_clone_args kargs;
+	pid_t set_tid[MAX_PID_NS_LEVEL];
+
+	kargs.set_tid = set_tid;
 
 	err = copy_clone_args_from_user(&kargs, uargs, size);
 	if (err)
diff --git a/kernel/pid.c b/kernel/pid.c
index 0a9f2e437217655daf18aaba0e57b30096595371..2278e249141dbad205f598c5857e6ea83b159077 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -157,7 +157,8 @@ void free_pid(struct pid *pid)
 	call_rcu(&pid->rcu, delayed_put_pid);
 }
 
-struct pid *alloc_pid(struct pid_namespace *ns)
+struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
+		      size_t set_tid_size)
 {
 	struct pid *pid;
 	enum pid_type type;
@@ -166,6 +167,17 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 	struct upid *upid;
 	int retval = -ENOMEM;
 
+	/*
+	 * set_tid_size contains the size of the set_tid array. Starting at
+	 * the most nested currently active PID namespace it tells alloc_pid()
+	 * which PID to set for a process in that most nested PID namespace
+	 * up to set_tid_size PID namespaces. It does not have to set the PID
+	 * for a process in all nested PID namespaces but set_tid_size must
+	 * never be greater than the current ns->level + 1.
+	 */
+	if (set_tid_size > ns->level + 1)
+		return ERR_PTR(-EINVAL);
+
 	pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
 	if (!pid)
 		return ERR_PTR(retval);
@@ -174,24 +186,54 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 	pid->level = ns->level;
 
 	for (i = ns->level; i >= 0; i--) {
-		int pid_min = 1;
+		int tid = 0;
+
+		if (set_tid_size) {
+			tid = set_tid[ns->level - i];
+
+			retval = -EINVAL;
+			if (tid < 1 || tid >= pid_max)
+				goto out_free;
+			/*
+			 * Also fail if a PID != 1 is requested and
+			 * no PID 1 exists.
+			 */
+			if (tid != 1 && !tmp->child_reaper)
+				goto out_free;
+			retval = -EPERM;
+			if (!ns_capable(tmp->user_ns, CAP_SYS_ADMIN))
+				goto out_free;
+			set_tid_size--;
+		}
 
 		idr_preload(GFP_KERNEL);
 		spin_lock_irq(&pidmap_lock);
 
-		/*
-		 * init really needs pid 1, but after reaching the maximum
-		 * wrap back to RESERVED_PIDS
-		 */
-		if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
-			pid_min = RESERVED_PIDS;
-
-		/*
-		 * Store a null pointer so find_pid_ns does not find
-		 * a partially initialized PID (see below).
-		 */
-		nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
-				      pid_max, GFP_ATOMIC);
+		if (tid) {
+			nr = idr_alloc(&tmp->idr, NULL, tid,
+				       tid + 1, GFP_ATOMIC);
+			/*
+			 * If ENOSPC is returned it means that the PID is
+			 * alreay in use. Return EEXIST in that case.
+			 */
+			if (nr == -ENOSPC)
+				nr = -EEXIST;
+		} else {
+			int pid_min = 1;
+			/*
+			 * init really needs pid 1, but after reaching the
+			 * maximum wrap back to RESERVED_PIDS
+			 */
+			if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
+				pid_min = RESERVED_PIDS;
+
+			/*
+			 * Store a null pointer so find_pid_ns does not find
+			 * a partially initialized PID (see below).
+			 */
+			nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
+					      pid_max, GFP_ATOMIC);
+		}
 		spin_unlock_irq(&pidmap_lock);
 		idr_preload_end();
 
@@ -299,7 +341,7 @@ static void __change_pid(struct task_struct *task, enum pid_type type,
 	*pid_ptr = new;
 
 	for (tmp = PIDTYPE_MAX; --tmp >= 0; )
-		if (!hlist_empty(&pid->tasks[tmp]))
+		if (pid_has_task(pid, tmp))
 			return;
 
 	free_pid(pid);
@@ -497,7 +539,7 @@ static int pidfd_create(struct pid *pid)
  */
 SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
 {
-	int fd, ret;
+	int fd;
 	struct pid *p;
 
 	if (flags)
@@ -510,13 +552,11 @@ SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
 	if (!p)
 		return -ESRCH;
 
-	ret = 0;
-	rcu_read_lock();
-	if (!pid_task(p, PIDTYPE_TGID))
-		ret = -EINVAL;
-	rcu_read_unlock();
+	if (pid_has_task(p, PIDTYPE_TGID))
+		fd = pidfd_create(p);
+	else
+		fd = -EINVAL;
 
-	fd = ret ?: pidfd_create(p);
 	put_pid(p);
 	return fd;
 }
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index a6a79f85c81a8972d1c9c3674aea9aeff691f192..d40017e79ebe505174693bdeeb936f442ee66938 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -26,8 +26,6 @@
 
 static DEFINE_MUTEX(pid_caches_mutex);
 static struct kmem_cache *pid_ns_cachep;
-/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
-#define MAX_PID_NS_LEVEL 32
 /* Write once array, filled from the beginning. */
 static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL];
 
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 0b6b81ba4421d45ba444896356a80c2d8fe07b9c..0fb95f25944d1bc3191beba7f1f455c737453022 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -5,6 +5,7 @@ TARGETS += bpf
 TARGETS += breakpoints
 TARGETS += capabilities
 TARGETS += cgroup
+TARGETS += clone3
 TARGETS += cpufreq
 TARGETS += cpu-hotplug
 TARGETS += drivers/dma-buf
diff --git a/tools/testing/selftests/clone3/.gitignore b/tools/testing/selftests/clone3/.gitignore
new file mode 100644
index 0000000000000000000000000000000000000000..0dc4f32c6cb89755ed824baf100f8cdde8923543
--- /dev/null
+++ b/tools/testing/selftests/clone3/.gitignore
@@ -0,0 +1,3 @@
+clone3
+clone3_clear_sighand
+clone3_set_tid
diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..cf976c732906d0657d2cdfc89900242cbb2a3ebb
--- /dev/null
+++ b/tools/testing/selftests/clone3/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+CFLAGS += -g -I../../../../usr/include/
+
+TEST_GEN_PROGS := clone3 clone3_clear_sighand clone3_set_tid
+
+include ../lib.mk
diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c
new file mode 100644
index 0000000000000000000000000000000000000000..f14c269a5a184bc786f66efb6f1fe9ae59b7b1f2
--- /dev/null
+++ b/tools/testing/selftests/clone3/clone3.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* Based on Christian Brauner's clone3() example */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <inttypes.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <sched.h>
+
+#include "../kselftest.h"
+#include "clone3_selftests.h"
+
+/*
+ * Different sizes of struct clone_args
+ */
+#ifndef CLONE3_ARGS_SIZE_V0
+#define CLONE3_ARGS_SIZE_V0 64
+#endif
+
+enum test_mode {
+	CLONE3_ARGS_NO_TEST,
+	CLONE3_ARGS_ALL_0,
+	CLONE3_ARGS_INVAL_EXIT_SIGNAL_BIG,
+	CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG,
+	CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG,
+	CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG,
+};
+
+static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
+{
+	struct clone_args args = {
+		.flags = flags,
+		.exit_signal = SIGCHLD,
+	};
+
+	struct clone_args_extended {
+		struct clone_args args;
+		__aligned_u64 excess_space[2];
+	} args_ext;
+
+	pid_t pid = -1;
+	int status;
+
+	memset(&args_ext, 0, sizeof(args_ext));
+	if (size > sizeof(struct clone_args))
+		args_ext.excess_space[1] = 1;
+
+	if (size == 0)
+		size = sizeof(struct clone_args);
+
+	switch (test_mode) {
+	case CLONE3_ARGS_ALL_0:
+		args.flags = 0;
+		args.exit_signal = 0;
+		break;
+	case CLONE3_ARGS_INVAL_EXIT_SIGNAL_BIG:
+		args.exit_signal = 0xbadc0ded00000000ULL;
+		break;
+	case CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG:
+		args.exit_signal = 0x0000000080000000ULL;
+		break;
+	case CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG:
+		args.exit_signal = 0x0000000000000100ULL;
+		break;
+	case CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG:
+		args.exit_signal = 0x00000000000000f0ULL;
+		break;
+	}
+
+	memcpy(&args_ext.args, &args, sizeof(struct clone_args));
+
+	pid = sys_clone3((struct clone_args *)&args_ext, size);
+	if (pid < 0) {
+		ksft_print_msg("%s - Failed to create new process\n",
+				strerror(errno));
+		return -errno;
+	}
+
+	if (pid == 0) {
+		ksft_print_msg("I am the child, my PID is %d\n", getpid());
+		_exit(EXIT_SUCCESS);
+	}
+
+	ksft_print_msg("I am the parent (%d). My child's pid is %d\n",
+			getpid(), pid);
+
+	if (waitpid(-1, &status, __WALL) < 0) {
+		ksft_print_msg("Child returned %s\n", strerror(errno));
+		return -errno;
+	}
+	if (WEXITSTATUS(status))
+		return WEXITSTATUS(status);
+
+	return 0;
+}
+
+static void test_clone3(uint64_t flags, size_t size, int expected,
+		       enum test_mode test_mode)
+{
+	int ret;
+
+	ksft_print_msg(
+		"[%d] Trying clone3() with flags %#" PRIx64 " (size %zu)\n",
+		getpid(), flags, size);
+	ret = call_clone3(flags, size, test_mode);
+	ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n",
+			getpid(), ret, expected);
+	if (ret != expected)
+		ksft_test_result_fail(
+			"[%d] Result (%d) is different than expected (%d)\n",
+			getpid(), ret, expected);
+	else
+		ksft_test_result_pass(
+			"[%d] Result (%d) matches expectation (%d)\n",
+			getpid(), ret, expected);
+}
+
+int main(int argc, char *argv[])
+{
+	pid_t pid;
+
+	uid_t uid = getuid();
+
+	test_clone3_supported();
+	ksft_print_header();
+	ksft_set_plan(17);
+
+	/* Just a simple clone3() should return 0.*/
+	test_clone3(0, 0, 0, CLONE3_ARGS_NO_TEST);
+
+	/* Do a clone3() in a new PID NS.*/
+	if (uid == 0)
+		test_clone3(CLONE_NEWPID, 0, 0, CLONE3_ARGS_NO_TEST);
+	else
+		ksft_test_result_skip("Skipping clone3() with CLONE_NEWPID\n");
+
+	/* Do a clone3() with CLONE3_ARGS_SIZE_V0. */
+	test_clone3(0, CLONE3_ARGS_SIZE_V0, 0, CLONE3_ARGS_NO_TEST);
+
+	/* Do a clone3() with CLONE3_ARGS_SIZE_V0 - 8 */
+	test_clone3(0, CLONE3_ARGS_SIZE_V0 - 8, -EINVAL, CLONE3_ARGS_NO_TEST);
+
+	/* Do a clone3() with sizeof(struct clone_args) + 8 */
+	test_clone3(0, sizeof(struct clone_args) + 8, 0, CLONE3_ARGS_NO_TEST);
+
+	/* Do a clone3() with exit_signal having highest 32 bits non-zero */
+	test_clone3(0, 0, -EINVAL, CLONE3_ARGS_INVAL_EXIT_SIGNAL_BIG);
+
+	/* Do a clone3() with negative 32-bit exit_signal */
+	test_clone3(0, 0, -EINVAL, CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG);
+
+	/* Do a clone3() with exit_signal not fitting into CSIGNAL mask */
+	test_clone3(0, 0, -EINVAL, CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG);
+
+	/* Do a clone3() with NSIG < exit_signal < CSIG */
+	test_clone3(0, 0, -EINVAL, CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG);
+
+	test_clone3(0, sizeof(struct clone_args) + 8, 0, CLONE3_ARGS_ALL_0);
+
+	test_clone3(0, sizeof(struct clone_args) + 16, -E2BIG,
+			CLONE3_ARGS_ALL_0);
+
+	test_clone3(0, sizeof(struct clone_args) * 2, -E2BIG,
+			CLONE3_ARGS_ALL_0);
+
+	/* Do a clone3() with > page size */
+	test_clone3(0, getpagesize() + 8, -E2BIG, CLONE3_ARGS_NO_TEST);
+
+	/* Do a clone3() with CLONE3_ARGS_SIZE_V0 in a new PID NS. */
+	if (uid == 0)
+		test_clone3(CLONE_NEWPID, CLONE3_ARGS_SIZE_V0, 0,
+				CLONE3_ARGS_NO_TEST);
+	else
+		ksft_test_result_skip("Skipping clone3() with CLONE_NEWPID\n");
+
+	/* Do a clone3() with CLONE3_ARGS_SIZE_V0 - 8 in a new PID NS */
+	test_clone3(CLONE_NEWPID, CLONE3_ARGS_SIZE_V0 - 8, -EINVAL,
+			CLONE3_ARGS_NO_TEST);
+
+	/* Do a clone3() with sizeof(struct clone_args) + 8 in a new PID NS */
+	if (uid == 0)
+		test_clone3(CLONE_NEWPID, sizeof(struct clone_args) + 8, 0,
+				CLONE3_ARGS_NO_TEST);
+	else
+		ksft_test_result_skip("Skipping clone3() with CLONE_NEWPID\n");
+
+	/* Do a clone3() with > page size in a new PID NS */
+	test_clone3(CLONE_NEWPID, getpagesize() + 8, -E2BIG,
+			CLONE3_ARGS_NO_TEST);
+
+	return !ksft_get_fail_cnt() ? ksft_exit_pass() : ksft_exit_fail();
+}
diff --git a/tools/testing/selftests/clone3/clone3_clear_sighand.c b/tools/testing/selftests/clone3/clone3_clear_sighand.c
new file mode 100644
index 0000000000000000000000000000000000000000..9e1af8aa769860242aad4ffc84b7c2fa86dbd242
--- /dev/null
+++ b/tools/testing/selftests/clone3/clone3_clear_sighand.c
@@ -0,0 +1,129 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <sys/syscall.h>
+#include <sys/wait.h>
+
+#include "../kselftest.h"
+#include "clone3_selftests.h"
+
+#ifndef CLONE_CLEAR_SIGHAND
+#define CLONE_CLEAR_SIGHAND 0x100000000ULL
+#endif
+
+static void nop_handler(int signo)
+{
+}
+
+static int wait_for_pid(pid_t pid)
+{
+	int status, ret;
+
+again:
+	ret = waitpid(pid, &status, 0);
+	if (ret == -1) {
+		if (errno == EINTR)
+			goto again;
+
+		return -1;
+	}
+
+	if (!WIFEXITED(status))
+		return -1;
+
+	return WEXITSTATUS(status);
+}
+
+static void test_clone3_clear_sighand(void)
+{
+	int ret;
+	pid_t pid;
+	struct clone_args args = {};
+	struct sigaction act;
+
+	/*
+	 * Check that CLONE_CLEAR_SIGHAND and CLONE_SIGHAND are mutually
+	 * exclusive.
+	 */
+	args.flags |= CLONE_CLEAR_SIGHAND | CLONE_SIGHAND;
+	args.exit_signal = SIGCHLD;
+	pid = sys_clone3(&args, sizeof(args));
+	if (pid > 0)
+		ksft_exit_fail_msg(
+			"clone3(CLONE_CLEAR_SIGHAND | CLONE_SIGHAND) succeeded\n");
+
+	act.sa_handler = nop_handler;
+	ret = sigemptyset(&act.sa_mask);
+	if (ret < 0)
+		ksft_exit_fail_msg("%s - sigemptyset() failed\n",
+				   strerror(errno));
+
+	act.sa_flags = 0;
+
+	/* Register signal handler for SIGUSR1 */
+	ret = sigaction(SIGUSR1, &act, NULL);
+	if (ret < 0)
+		ksft_exit_fail_msg(
+			"%s - sigaction(SIGUSR1, &act, NULL) failed\n",
+			strerror(errno));
+
+	/* Register signal handler for SIGUSR2 */
+	ret = sigaction(SIGUSR2, &act, NULL);
+	if (ret < 0)
+		ksft_exit_fail_msg(
+			"%s - sigaction(SIGUSR2, &act, NULL) failed\n",
+			strerror(errno));
+
+	/* Check that CLONE_CLEAR_SIGHAND works. */
+	args.flags = CLONE_CLEAR_SIGHAND;
+	pid = sys_clone3(&args, sizeof(args));
+	if (pid < 0)
+		ksft_exit_fail_msg("%s - clone3(CLONE_CLEAR_SIGHAND) failed\n",
+				   strerror(errno));
+
+	if (pid == 0) {
+		ret = sigaction(SIGUSR1, NULL, &act);
+		if (ret < 0)
+			exit(EXIT_FAILURE);
+
+		if (act.sa_handler != SIG_DFL)
+			exit(EXIT_FAILURE);
+
+		ret = sigaction(SIGUSR2, NULL, &act);
+		if (ret < 0)
+			exit(EXIT_FAILURE);
+
+		if (act.sa_handler != SIG_DFL)
+			exit(EXIT_FAILURE);
+
+		exit(EXIT_SUCCESS);
+	}
+
+	ret = wait_for_pid(pid);
+	if (ret)
+		ksft_exit_fail_msg(
+			"Failed to clear signal handler for child process\n");
+
+	ksft_test_result_pass("Cleared signal handlers for child process\n");
+}
+
+int main(int argc, char **argv)
+{
+	ksft_print_header();
+	test_clone3_supported();
+
+	ksft_set_plan(1);
+
+	test_clone3_clear_sighand();
+
+	return ksft_exit_pass();
+}
diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/testing/selftests/clone3/clone3_selftests.h
new file mode 100644
index 0000000000000000000000000000000000000000..a3f2c8ad8bcc3a35e6d45090648be2f1b9799816
--- /dev/null
+++ b/tools/testing/selftests/clone3/clone3_selftests.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _CLONE3_SELFTESTS_H
+#define _CLONE3_SELFTESTS_H
+
+#define _GNU_SOURCE
+#include <sched.h>
+#include <stdint.h>
+#include <syscall.h>
+#include <linux/types.h>
+
+#define ptr_to_u64(ptr) ((__u64)((uintptr_t)(ptr)))
+
+#ifndef __NR_clone3
+#define __NR_clone3 -1
+struct clone_args {
+	__aligned_u64 flags;
+	__aligned_u64 pidfd;
+	__aligned_u64 child_tid;
+	__aligned_u64 parent_tid;
+	__aligned_u64 exit_signal;
+	__aligned_u64 stack;
+	__aligned_u64 stack_size;
+	__aligned_u64 tls;
+	__aligned_u64 set_tid;
+	__aligned_u64 set_tid_size;
+};
+#endif
+
+static pid_t sys_clone3(struct clone_args *args, size_t size)
+{
+	fflush(stdout);
+	fflush(stderr);
+	return syscall(__NR_clone3, args, size);
+}
+
+static inline void test_clone3_supported(void)
+{
+	pid_t pid;
+	struct clone_args args = {};
+
+	if (__NR_clone3 < 0)
+		ksft_exit_skip("clone3() syscall is not supported\n");
+
+	/* Set to something that will always cause EINVAL. */
+	args.exit_signal = -1;
+	pid = sys_clone3(&args, sizeof(args));
+	if (!pid)
+		exit(EXIT_SUCCESS);
+
+	if (pid > 0) {
+		wait(NULL);
+		ksft_exit_fail_msg(
+			"Managed to create child process with invalid exit_signal\n");
+	}
+
+	if (errno == ENOSYS)
+		ksft_exit_skip("clone3() syscall is not supported\n");
+
+	ksft_print_msg("clone3() syscall supported\n");
+}
+
+#endif /* _CLONE3_SELFTESTS_H */
diff --git a/tools/testing/selftests/clone3/clone3_set_tid.c b/tools/testing/selftests/clone3/clone3_set_tid.c
new file mode 100644
index 0000000000000000000000000000000000000000..25beb22f35b50d9affe29feed3cb88df1b0fd757
--- /dev/null
+++ b/tools/testing/selftests/clone3/clone3_set_tid.c
@@ -0,0 +1,397 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Based on Christian Brauner's clone3() example.
+ * These tests are assuming to be running in the host's
+ * PID namespace.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <sched.h>
+
+#include "../kselftest.h"
+#include "clone3_selftests.h"
+
+#ifndef MAX_PID_NS_LEVEL
+#define MAX_PID_NS_LEVEL 32
+#endif
+
+static int pipe_1[2];
+static int pipe_2[2];
+
+static void child_exit(int ret)
+{
+	fflush(stdout);
+	fflush(stderr);
+	_exit(ret);
+}
+
+static int call_clone3_set_tid(pid_t *set_tid,
+			       size_t set_tid_size,
+			       int flags,
+			       int expected_pid,
+			       bool wait_for_it)
+{
+	int status;
+	pid_t pid = -1;
+
+	struct clone_args args = {
+		.flags = flags,
+		.exit_signal = SIGCHLD,
+		.set_tid = ptr_to_u64(set_tid),
+		.set_tid_size = set_tid_size,
+	};
+
+	pid = sys_clone3(&args, sizeof(struct clone_args));
+	if (pid < 0) {
+		ksft_print_msg("%s - Failed to create new process\n",
+			       strerror(errno));
+		return -errno;
+	}
+
+	if (pid == 0) {
+		int ret;
+		char tmp = 0;
+		int exit_code = EXIT_SUCCESS;
+
+		ksft_print_msg("I am the child, my PID is %d (expected %d)\n",
+			       getpid(), set_tid[0]);
+		if (wait_for_it) {
+			ksft_print_msg("[%d] Child is ready and waiting\n",
+				       getpid());
+
+			/* Signal the parent that the child is ready */
+			close(pipe_1[0]);
+			ret = write(pipe_1[1], &tmp, 1);
+			if (ret != 1) {
+				ksft_print_msg(
+					"Writing to pipe returned %d", ret);
+				exit_code = EXIT_FAILURE;
+			}
+			close(pipe_1[1]);
+			close(pipe_2[1]);
+			ret = read(pipe_2[0], &tmp, 1);
+			if (ret != 1) {
+				ksft_print_msg(
+					"Reading from pipe returned %d", ret);
+				exit_code = EXIT_FAILURE;
+			}
+			close(pipe_2[0]);
+		}
+
+		if (set_tid[0] != getpid())
+			child_exit(EXIT_FAILURE);
+		child_exit(exit_code);
+	}
+
+	if (expected_pid == 0 || expected_pid == pid) {
+		ksft_print_msg("I am the parent (%d). My child's pid is %d\n",
+			       getpid(), pid);
+	} else {
+		ksft_print_msg(
+			"Expected child pid %d does not match actual pid %d\n",
+			expected_pid, pid);
+		return -1;
+	}
+
+	if (waitpid(pid, &status, 0) < 0) {
+		ksft_print_msg("Child returned %s\n", strerror(errno));
+		return -errno;
+	}
+
+	if (!WIFEXITED(status))
+		return -1;
+
+	return WEXITSTATUS(status);
+}
+
+static void test_clone3_set_tid(pid_t *set_tid,
+				size_t set_tid_size,
+				int flags,
+				int expected,
+				int expected_pid,
+				bool wait_for_it)
+{
+	int ret;
+
+	ksft_print_msg(
+		"[%d] Trying clone3() with CLONE_SET_TID to %d and 0x%x\n",
+		getpid(), set_tid[0], flags);
+	ret = call_clone3_set_tid(set_tid, set_tid_size, flags, expected_pid,
+				  wait_for_it);
+	ksft_print_msg(
+		"[%d] clone3() with CLONE_SET_TID %d says :%d - expected %d\n",
+		getpid(), set_tid[0], ret, expected);
+	if (ret != expected)
+		ksft_test_result_fail(
+			"[%d] Result (%d) is different than expected (%d)\n",
+			getpid(), ret, expected);
+	else
+		ksft_test_result_pass(
+			"[%d] Result (%d) matches expectation (%d)\n",
+			getpid(), ret, expected);
+}
+int main(int argc, char *argv[])
+{
+	FILE *f;
+	char buf;
+	char *line;
+	int status;
+	int ret = -1;
+	size_t len = 0;
+	int pid_max = 0;
+	uid_t uid = getuid();
+	char proc_path[100] = {0};
+	pid_t pid, ns1, ns2, ns3, ns_pid;
+	pid_t set_tid[MAX_PID_NS_LEVEL * 2];
+
+	ksft_print_header();
+	test_clone3_supported();
+	ksft_set_plan(29);
+
+	if (pipe(pipe_1) < 0 || pipe(pipe_2) < 0)
+		ksft_exit_fail_msg("pipe() failed\n");
+
+	f = fopen("/proc/sys/kernel/pid_max", "r");
+	if (f == NULL)
+		ksft_exit_fail_msg(
+			"%s - Could not open /proc/sys/kernel/pid_max\n",
+			strerror(errno));
+	fscanf(f, "%d", &pid_max);
+	fclose(f);
+	ksft_print_msg("/proc/sys/kernel/pid_max %d\n", pid_max);
+
+	/* Try invalid settings */
+	memset(&set_tid, 0, sizeof(set_tid));
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL + 1, 0, -EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0,
+			-EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 0, -EINVAL, 0, 0);
+
+	/*
+	 * This can actually work if this test running in a MAX_PID_NS_LEVEL - 1
+	 * nested PID namespace.
+	 */
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL - 1, 0, -EINVAL, 0, 0);
+
+	memset(&set_tid, 0xff, sizeof(set_tid));
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL + 1, 0, -EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0,
+			-EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 0, -EINVAL, 0, 0);
+
+	/*
+	 * This can actually work if this test running in a MAX_PID_NS_LEVEL - 1
+	 * nested PID namespace.
+	 */
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL - 1, 0, -EINVAL, 0, 0);
+
+	memset(&set_tid, 0, sizeof(set_tid));
+	/* Try with an invalid PID */
+	set_tid[0] = 0;
+	test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+
+	set_tid[0] = -1;
+	test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+
+	/* Claim that the set_tid array actually contains 2 elements. */
+	test_clone3_set_tid(set_tid, 2, 0, -EINVAL, 0, 0);
+
+	/* Try it in a new PID namespace */
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
+	else
+		ksft_test_result_skip("Clone3() with set_tid requires root\n");
+
+	/* Try with a valid PID (1) this should return -EEXIST. */
+	set_tid[0] = 1;
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, 0, -EEXIST, 0, 0);
+	else
+		ksft_test_result_skip("Clone3() with set_tid requires root\n");
+
+	/* Try it in a new PID namespace */
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, 0, 0, 0);
+	else
+		ksft_test_result_skip("Clone3() with set_tid requires root\n");
+
+	/* pid_max should fail everywhere */
+	set_tid[0] = pid_max;
+	test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
+	else
+		ksft_test_result_skip("Clone3() with set_tid requires root\n");
+
+	if (uid != 0) {
+		/*
+		 * All remaining tests require root. Tell the framework
+		 * that all those tests are skipped as non-root.
+		 */
+		ksft_cnt.ksft_xskip += ksft_plan - ksft_test_num();
+		goto out;
+	}
+
+	/* Find the current active PID */
+	pid = fork();
+	if (pid == 0) {
+		ksft_print_msg("Child has PID %d\n", getpid());
+		child_exit(EXIT_SUCCESS);
+	}
+	if (waitpid(pid, &status, 0) < 0)
+		ksft_exit_fail_msg("Waiting for child %d failed", pid);
+
+	/* After the child has finished, its PID should be free. */
+	set_tid[0] = pid;
+	test_clone3_set_tid(set_tid, 1, 0, 0, 0, 0);
+
+	/* This should fail as there is no PID 1 in that namespace */
+	test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
+
+	/*
+	 * Creating a process with PID 1 in the newly created most nested
+	 * PID namespace and PID 'pid' in the parent PID namespace. This
+	 * needs to work.
+	 */
+	set_tid[0] = 1;
+	set_tid[1] = pid;
+	test_clone3_set_tid(set_tid, 2, CLONE_NEWPID, 0, pid, 0);
+
+	ksft_print_msg("unshare PID namespace\n");
+	if (unshare(CLONE_NEWPID) == -1)
+		ksft_exit_fail_msg("unshare(CLONE_NEWPID) failed: %s\n",
+				strerror(errno));
+
+	set_tid[0] = pid;
+
+	/* This should fail as there is no PID 1 in that namespace */
+	test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+
+	/* Let's create a PID 1 */
+	ns_pid = fork();
+	if (ns_pid == 0) {
+		/*
+		 * This and the next test cases check that all pid-s are
+		 * released on error paths.
+		 */
+		set_tid[0] = 43;
+		set_tid[1] = -1;
+		test_clone3_set_tid(set_tid, 2, 0, -EINVAL, 0, 0);
+
+		set_tid[0] = 43;
+		set_tid[1] = pid;
+		test_clone3_set_tid(set_tid, 2, 0, 0, 43, 0);
+
+		ksft_print_msg("Child in PID namespace has PID %d\n", getpid());
+		set_tid[0] = 2;
+		test_clone3_set_tid(set_tid, 1, 0, 0, 2, 0);
+
+		set_tid[0] = 1;
+		set_tid[1] = -1;
+		set_tid[2] = pid;
+		/* This should fail as there is invalid PID at level '1'. */
+		test_clone3_set_tid(set_tid, 3, CLONE_NEWPID, -EINVAL, 0, 0);
+
+		set_tid[0] = 1;
+		set_tid[1] = 42;
+		set_tid[2] = pid;
+		/*
+		 * This should fail as there are not enough active PID
+		 * namespaces. Again assuming this is running in the host's
+		 * PID namespace. Not yet nested.
+		 */
+		test_clone3_set_tid(set_tid, 4, CLONE_NEWPID, -EINVAL, 0, 0);
+
+		/*
+		 * This should work and from the parent we should see
+		 * something like 'NSpid:	pid	42	1'.
+		 */
+		test_clone3_set_tid(set_tid, 3, CLONE_NEWPID, 0, 42, true);
+
+		child_exit(ksft_cnt.ksft_fail);
+	}
+
+	close(pipe_1[1]);
+	close(pipe_2[0]);
+	while (read(pipe_1[0], &buf, 1) > 0) {
+		ksft_print_msg("[%d] Child is ready and waiting\n", getpid());
+		break;
+	}
+
+	snprintf(proc_path, sizeof(proc_path), "/proc/%d/status", pid);
+	f = fopen(proc_path, "r");
+	if (f == NULL)
+		ksft_exit_fail_msg(
+			"%s - Could not open %s\n",
+			strerror(errno), proc_path);
+
+	while (getline(&line, &len, f) != -1) {
+		if (strstr(line, "NSpid")) {
+			int i;
+
+			/* Verify that all generated PIDs are as expected. */
+			i = sscanf(line, "NSpid:\t%d\t%d\t%d",
+				   &ns3, &ns2, &ns1);
+			if (i != 3) {
+				ksft_print_msg(
+					"Unexpected 'NSPid:' entry: %s",
+					line);
+				ns1 = ns2 = ns3 = 0;
+			}
+			break;
+		}
+	}
+	fclose(f);
+	free(line);
+	close(pipe_2[0]);
+
+	/* Tell the clone3()'d child to finish. */
+	write(pipe_2[1], &buf, 1);
+	close(pipe_2[1]);
+
+	if (waitpid(ns_pid, &status, 0) < 0) {
+		ksft_print_msg("Child returned %s\n", strerror(errno));
+		ret = -errno;
+		goto out;
+	}
+
+	if (!WIFEXITED(status))
+		ksft_test_result_fail("Child error\n");
+
+	ksft_cnt.ksft_pass += 6 - (ksft_cnt.ksft_fail - WEXITSTATUS(status));
+	ksft_cnt.ksft_fail = WEXITSTATUS(status);
+
+	if (ns3 == pid && ns2 == 42 && ns1 == 1)
+		ksft_test_result_pass(
+			"PIDs in all namespaces as expected (%d,%d,%d)\n",
+			ns3, ns2, ns1);
+	else
+		ksft_test_result_fail(
+			"PIDs in all namespaces not as expected (%d,%d,%d)\n",
+			ns3, ns2, ns1);
+out:
+	ret = 0;
+
+	return !ret ? ksft_exit_pass() : ksft_exit_fail();
+}
diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile
index 7550f08822a3345290e2c780517c0b7cc373d43d..43db1b98e8459f3ebef95fee079db5fef0ed15e6 100644
--- a/tools/testing/selftests/pidfd/Makefile
+++ b/tools/testing/selftests/pidfd/Makefile
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 CFLAGS += -g -I../../../../usr/include/ -pthread
 
-TEST_GEN_PROGS := pidfd_test pidfd_open_test pidfd_poll_test pidfd_wait
+TEST_GEN_PROGS := pidfd_test pidfd_fdinfo_test pidfd_open_test pidfd_poll_test pidfd_wait
 
 include ../lib.mk
 
diff --git a/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c b/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c
new file mode 100644
index 0000000000000000000000000000000000000000..22558524f71c34da86e9e0dacc5a73c523254e72
--- /dev/null
+++ b/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c
@@ -0,0 +1,296 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/types.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <sys/wait.h>
+
+#include "pidfd.h"
+#include "../kselftest.h"
+
+struct error {
+	int  code;
+	char msg[512];
+};
+
+static int error_set(struct error *err, int code, const char *fmt, ...)
+{
+	va_list args;
+	int r;
+
+	if (code == PIDFD_PASS || !err || err->code != PIDFD_PASS)
+		return code;
+
+	err->code = code;
+	va_start(args, fmt);
+	r = vsnprintf(err->msg, sizeof(err->msg), fmt, args);
+	assert((size_t)r < sizeof(err->msg));
+	va_end(args);
+
+	return code;
+}
+
+static void error_report(struct error *err, const char *test_name)
+{
+	switch (err->code) {
+	case PIDFD_ERROR:
+		ksft_exit_fail_msg("%s test: Fatal: %s\n", test_name, err->msg);
+		break;
+
+	case PIDFD_FAIL:
+		/* will be: not ok %d # error %s test: %s */
+		ksft_test_result_error("%s test: %s\n", test_name, err->msg);
+		break;
+
+	case PIDFD_SKIP:
+		/* will be: not ok %d # SKIP %s test: %s */
+		ksft_test_result_skip("%s test: %s\n", test_name, err->msg);
+		break;
+
+	case PIDFD_XFAIL:
+		ksft_test_result_pass("%s test: Expected failure: %s\n",
+				      test_name, err->msg);
+		break;
+
+	case PIDFD_PASS:
+		ksft_test_result_pass("%s test: Passed\n");
+		break;
+
+	default:
+		ksft_exit_fail_msg("%s test: Unknown code: %d %s\n",
+				   test_name, err->code, err->msg);
+		break;
+	}
+}
+
+static inline int error_check(struct error *err, const char *test_name)
+{
+	/* In case of error we bail out and terminate the test program */
+	if (err->code == PIDFD_ERROR)
+		error_report(err, test_name);
+
+	return err->code;
+}
+
+struct child {
+	pid_t pid;
+	int   fd;
+};
+
+static struct child clone_newns(int (*fn)(void *), void *args,
+				struct error *err)
+{
+	static int flags = CLONE_PIDFD | CLONE_NEWPID | CLONE_NEWNS | SIGCHLD;
+	size_t stack_size = 1024;
+	char *stack[1024] = { 0 };
+	struct child ret;
+
+	if (!(flags & CLONE_NEWUSER) && geteuid() != 0)
+		flags |= CLONE_NEWUSER;
+
+#ifdef __ia64__
+	ret.pid = __clone2(fn, stack, stack_size, flags, args, &ret.fd);
+#else
+	ret.pid = clone(fn, stack + stack_size, flags, args, &ret.fd);
+#endif
+
+	if (ret.pid < 0) {
+		error_set(err, PIDFD_ERROR, "clone failed (ret %d, errno %d)",
+			  ret.fd, errno);
+		return ret;
+	}
+
+	ksft_print_msg("New child: %d, fd: %d\n", ret.pid, ret.fd);
+
+	return ret;
+}
+
+static inline void child_close(struct child *child)
+{
+	close(child->fd);
+}
+
+static inline int child_join(struct child *child, struct error *err)
+{
+	int r;
+
+	r = wait_for_pid(child->pid);
+	if (r < 0)
+		error_set(err, PIDFD_ERROR, "waitpid failed (ret %d, errno %d)",
+			  r, errno);
+	else if (r > 0)
+		error_set(err, r, "child %d reported: %d", child->pid, r);
+
+	return r;
+}
+
+static inline int child_join_close(struct child *child, struct error *err)
+{
+	child_close(child);
+	return child_join(child, err);
+}
+
+static inline void trim_newline(char *str)
+{
+	char *pos = strrchr(str, '\n');
+
+	if (pos)
+		*pos = '\0';
+}
+
+static int verify_fdinfo(int pidfd, struct error *err, const char *prefix,
+			 size_t prefix_len, const char *expect, ...)
+{
+	char buffer[512] = {0, };
+	char path[512] = {0, };
+	va_list args;
+	FILE *f;
+	char *line = NULL;
+	size_t n = 0;
+	int found = 0;
+	int r;
+
+	va_start(args, expect);
+	r = vsnprintf(buffer, sizeof(buffer), expect, args);
+	assert((size_t)r < sizeof(buffer));
+	va_end(args);
+
+	snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", pidfd);
+	f = fopen(path, "re");
+	if (!f)
+		return error_set(err, PIDFD_ERROR, "fdinfo open failed for %d",
+				 pidfd);
+
+	while (getline(&line, &n, f) != -1) {
+		char *val;
+
+		if (strncmp(line, prefix, prefix_len))
+			continue;
+
+		found = 1;
+
+		val = line + prefix_len;
+		r = strcmp(val, buffer);
+		if (r != 0) {
+			trim_newline(line);
+			trim_newline(buffer);
+			error_set(err, PIDFD_FAIL, "%s '%s' != '%s'",
+				  prefix, val, buffer);
+		}
+		break;
+	}
+
+	free(line);
+	fclose(f);
+
+	if (found == 0)
+		return error_set(err, PIDFD_FAIL, "%s not found for fd %d",
+				 prefix, pidfd);
+
+	return PIDFD_PASS;
+}
+
+static int child_fdinfo_nspid_test(void *args)
+{
+	struct error err;
+	int pidfd;
+	int r;
+
+	/* if we got no fd for the sibling, we are done */
+	if (!args)
+		return PIDFD_PASS;
+
+	/* verify that we can not resolve the pidfd for a process
+	 * in a sibling pid namespace, i.e. a pid namespace it is
+	 * not in our or a descended namespace
+	 */
+	r = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0);
+	if (r < 0) {
+		ksft_print_msg("Failed to remount / private\n");
+		return PIDFD_ERROR;
+	}
+
+	(void)umount2("/proc", MNT_DETACH);
+	r = mount("proc", "/proc", "proc", 0, NULL);
+	if (r < 0) {
+		ksft_print_msg("Failed to remount /proc\n");
+		return PIDFD_ERROR;
+	}
+
+	pidfd = *(int *)args;
+	r = verify_fdinfo(pidfd, &err, "NSpid:", 6, "\t0\n");
+
+	if (r != PIDFD_PASS)
+		ksft_print_msg("NSpid fdinfo check failed: %s\n", err.msg);
+
+	return r;
+}
+
+static void test_pidfd_fdinfo_nspid(void)
+{
+	struct child a, b;
+	struct error err = {0, };
+	const char *test_name = "pidfd check for NSpid in fdinfo";
+
+	/* Create a new child in a new pid and mount namespace */
+	a = clone_newns(child_fdinfo_nspid_test, NULL, &err);
+	error_check(&err, test_name);
+
+	/* Pass the pidfd representing the first child to the
+	 * second child, which will be in a sibling pid namespace,
+	 * which means that the fdinfo NSpid entry for the pidfd
+	 * should only contain '0'.
+	 */
+	b = clone_newns(child_fdinfo_nspid_test, &a.fd, &err);
+	error_check(&err, test_name);
+
+	/* The children will have pid 1 in the new pid namespace,
+	 * so the line must be 'NSPid:\t<pid>\t1'.
+	 */
+	verify_fdinfo(a.fd, &err, "NSpid:", 6, "\t%d\t%d\n", a.pid, 1);
+	verify_fdinfo(b.fd, &err, "NSpid:", 6, "\t%d\t%d\n", b.pid, 1);
+
+	/* wait for the process, check the exit status and set
+	 * 'err' accordingly, if it is not already set.
+	 */
+	child_join_close(&a, &err);
+	child_join_close(&b, &err);
+
+	error_report(&err, test_name);
+}
+
+static void test_pidfd_dead_fdinfo(void)
+{
+	struct child a;
+	struct error err = {0, };
+	const char *test_name = "pidfd check fdinfo for dead process";
+
+	/* Create a new child in a new pid and mount namespace */
+	a = clone_newns(child_fdinfo_nspid_test, NULL, &err);
+	error_check(&err, test_name);
+	child_join(&a, &err);
+
+	verify_fdinfo(a.fd, &err, "Pid:", 4, "\t-1\n");
+	verify_fdinfo(a.fd, &err, "NSpid:", 6, "\t-1\n");
+	child_close(&a);
+	error_report(&err, test_name);
+}
+
+int main(int argc, char **argv)
+{
+	ksft_print_header();
+	ksft_set_plan(2);
+
+	test_pidfd_fdinfo_nspid();
+	test_pidfd_dead_fdinfo();
+
+	return ksft_exit_pass();
+}