1 files changed, 282 insertions, 105 deletions

diff --git a/kernel/pid.c b/kernel/pid.c
index 2fc0a16ec77b..a31771bc89c1 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -42,6 +42,8 @@
 #include <linux/sched/signal.h>
 #include <linux/sched/task.h>
 #include <linux/idr.h>
+#include <linux/pidfs.h>
+#include <linux/seqlock.h>
 #include <net/sock.h>
 #include <uapi/linux/pidfd.h>
 
@@ -59,12 +61,8 @@ struct pid init_struct_pid = {
 	}, }
 };
 
-int pid_max = PID_MAX_DEFAULT;
-
-#define RESERVED_PIDS		300
-
-int pid_max_min = RESERVED_PIDS + 1;
-int pid_max_max = PID_MAX_LIMIT;
+static int pid_max_min = RESERVED_PIDS + 1;
+static int pid_max_max = PID_MAX_LIMIT;
 
 /*
  * PID-map pages start out as NULL, they get allocated upon
@@ -73,34 +71,21 @@ int pid_max_max = PID_MAX_LIMIT;
  * the scheme scales to up to 4 million PIDs, runtime.
  */
 struct pid_namespace init_pid_ns = {
-	.ns.count = REFCOUNT_INIT(2),
+	.ns = NS_COMMON_INIT(init_pid_ns),
 	.idr = IDR_INIT(init_pid_ns.idr),
 	.pid_allocated = PIDNS_ADDING,
 	.level = 0,
 	.child_reaper = &init_task,
 	.user_ns = &init_user_ns,
-	.ns.inum = PROC_PID_INIT_INO,
-#ifdef CONFIG_PID_NS
-	.ns.ops = &pidns_operations,
+	.pid_max = PID_MAX_DEFAULT,
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
+	.memfd_noexec_scope = MEMFD_NOEXEC_SCOPE_EXEC,
 #endif
 };
 EXPORT_SYMBOL_GPL(init_pid_ns);
 
-/*
- * Note: disable interrupts while the pidmap_lock is held as an
- * interrupt might come in and do read_lock(&tasklist_lock).
- *
- * If we don't disable interrupts there is a nasty deadlock between
- * detach_pid()->free_pid() and another cpu that does
- * spin_lock(&pidmap_lock) followed by an interrupt routine that does
- * read_lock(&tasklist_lock);
- *
- * After we clean up the tasklist_lock and know there are no
- * irq handlers that take it we can leave the interrupts enabled.
- * For now it is easier to be safe than to prove it can't happen.
- */
-
 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
+seqcount_spinlock_t pidmap_lock_seq = SEQCNT_SPINLOCK_ZERO(pidmap_lock_seq, &pidmap_lock);
 
 void put_pid(struct pid *pid)
 {
@@ -111,6 +96,7 @@ void put_pid(struct pid *pid)
 
 	ns = pid->numbers[pid->level].ns;
 	if (refcount_dec_and_test(&pid->count)) {
+		pidfs_free_pid(pid);
 		kmem_cache_free(ns->pid_cachep, pid);
 		put_pid_ns(ns);
 	}
@@ -125,11 +111,15 @@ static void delayed_put_pid(struct rcu_head *rhp)
 
 void free_pid(struct pid *pid)
 {
-	/* We can be called with write_lock_irq(&tasklist_lock) held */
 	int i;
-	unsigned long flags;
+	struct pid_namespace *active_ns;
+
+	lockdep_assert_not_held(&tasklist_lock);
+
+	active_ns = pid->numbers[pid->level].ns;
+	ns_ref_active_put(active_ns);
 
-	spin_lock_irqsave(&pidmap_lock, flags);
+	spin_lock(&pidmap_lock);
 	for (i = 0; i <= pid->level; i++) {
 		struct upid *upid = pid->numbers + i;
 		struct pid_namespace *ns = upid->ns;
@@ -151,11 +141,24 @@ void free_pid(struct pid *pid)
 
 		idr_remove(&ns->idr, upid->nr);
 	}
-	spin_unlock_irqrestore(&pidmap_lock, flags);
+	pidfs_remove_pid(pid);
+	spin_unlock(&pidmap_lock);
 
 	call_rcu(&pid->rcu, delayed_put_pid);
 }
 
+void free_pids(struct pid **pids)
+{
+	int tmp;
+
+	/*
+	 * This can batch pidmap_lock.
+	 */
+	for (tmp = PIDTYPE_MAX; --tmp >= 0; )
+		if (pids[tmp])
+			free_pid(pids[tmp]);
+}
+
 struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
 		      size_t set_tid_size)
 {
@@ -186,6 +189,7 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
 
 	for (i = ns->level; i >= 0; i--) {
 		int tid = 0;
+		int pid_max = READ_ONCE(tmp->pid_max);
 
 		if (set_tid_size) {
 			tid = set_tid[ns->level - i];
@@ -206,7 +210,7 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
 		}
 
 		idr_preload(GFP_KERNEL);
-		spin_lock_irq(&pidmap_lock);
+		spin_lock(&pidmap_lock);
 
 		if (tid) {
 			nr = idr_alloc(&tmp->idr, NULL, tid,
@@ -233,7 +237,7 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
 			nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
 					      pid_max, GFP_ATOMIC);
 		}
-		spin_unlock_irq(&pidmap_lock);
+		spin_unlock(&pidmap_lock);
 		idr_preload_end();
 
 		if (nr < 0) {
@@ -266,24 +270,29 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
 	INIT_HLIST_HEAD(&pid->inodes);
 
 	upid = pid->numbers + ns->level;
-	spin_lock_irq(&pidmap_lock);
+	idr_preload(GFP_KERNEL);
+	spin_lock(&pidmap_lock);
 	if (!(ns->pid_allocated & PIDNS_ADDING))
 		goto out_unlock;
+	pidfs_add_pid(pid);
 	for ( ; upid >= pid->numbers; --upid) {
 		/* Make the PID visible to find_pid_ns. */
 		idr_replace(&upid->ns->idr, pid, upid->nr);
 		upid->ns->pid_allocated++;
 	}
-	spin_unlock_irq(&pidmap_lock);
+	spin_unlock(&pidmap_lock);
+	idr_preload_end();
+	ns_ref_active_get(ns);
 
 	return pid;
 
 out_unlock:
-	spin_unlock_irq(&pidmap_lock);
+	spin_unlock(&pidmap_lock);
+	idr_preload_end();
 	put_pid_ns(ns);
 
 out_free:
-	spin_lock_irq(&pidmap_lock);
+	spin_lock(&pidmap_lock);
 	while (++i <= ns->level) {
 		upid = pid->numbers + i;
 		idr_remove(&upid->ns->idr, upid->nr);
@@ -293,7 +302,7 @@ out_free:
 	if (ns->pid_allocated == PIDNS_ADDING)
 		idr_set_cursor(&ns->idr, 0);
 
-	spin_unlock_irq(&pidmap_lock);
+	spin_unlock(&pidmap_lock);
 
 	kmem_cache_free(ns->pid_cachep, pid);
 	return ERR_PTR(retval);
@@ -301,9 +310,9 @@ out_free:
 
 void disable_pid_allocation(struct pid_namespace *ns)
 {
-	spin_lock_irq(&pidmap_lock);
+	spin_lock(&pidmap_lock);
 	ns->pid_allocated &= ~PIDNS_ADDING;
-	spin_unlock_irq(&pidmap_lock);
+	spin_unlock(&pidmap_lock);
 }
 
 struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
@@ -330,17 +339,23 @@ static struct pid **task_pid_ptr(struct task_struct *task, enum pid_type type)
  */
 void attach_pid(struct task_struct *task, enum pid_type type)
 {
-	struct pid *pid = *task_pid_ptr(task, type);
+	struct pid *pid;
+
+	lockdep_assert_held_write(&tasklist_lock);
+
+	pid = *task_pid_ptr(task, type);
 	hlist_add_head_rcu(&task->pid_links[type], &pid->tasks[type]);
 }
 
-static void __change_pid(struct task_struct *task, enum pid_type type,
-			struct pid *new)
+static void __change_pid(struct pid **pids, struct task_struct *task,
+			 enum pid_type type, struct pid *new)
 {
-	struct pid **pid_ptr = task_pid_ptr(task, type);
-	struct pid *pid;
+	struct pid **pid_ptr, *pid;
 	int tmp;
 
+	lockdep_assert_held_write(&tasklist_lock);
+
+	pid_ptr = task_pid_ptr(task, type);
 	pid = *pid_ptr;
 
 	hlist_del_rcu(&task->pid_links[type]);
@@ -350,18 +365,19 @@ static void __change_pid(struct task_struct *task, enum pid_type type,
 		if (pid_has_task(pid, tmp))
 			return;
 
-	free_pid(pid);
+	WARN_ON(pids[type]);
+	pids[type] = pid;
 }
 
-void detach_pid(struct task_struct *task, enum pid_type type)
+void detach_pid(struct pid **pids, struct task_struct *task, enum pid_type type)
 {
-	__change_pid(task, type, NULL);
+	__change_pid(pids, task, type, NULL);
 }
 
-void change_pid(struct task_struct *task, enum pid_type type,
+void change_pid(struct pid **pids, struct task_struct *task, enum pid_type type,
 		struct pid *pid)
 {
-	__change_pid(task, type, pid);
+	__change_pid(pids, task, type, pid);
 	attach_pid(task, type);
 }
 
@@ -372,6 +388,8 @@ void exchange_tids(struct task_struct *left, struct task_struct *right)
 	struct hlist_head *head1 = &pid1->tasks[PIDTYPE_PID];
 	struct hlist_head *head2 = &pid2->tasks[PIDTYPE_PID];
 
+	lockdep_assert_held_write(&tasklist_lock);
+
 	/* Swap the single entry tid lists */
 	hlists_swap_heads_rcu(head1, head2);
 
@@ -388,8 +406,8 @@ void exchange_tids(struct task_struct *left, struct task_struct *right)
 void transfer_pid(struct task_struct *old, struct task_struct *new,
 			   enum pid_type type)
 {
-	if (type == PIDTYPE_PID)
-		new->thread_pid = old->thread_pid;
+	WARN_ON_ONCE(type == PIDTYPE_PID);
+	lockdep_assert_held_write(&tasklist_lock);
 	hlist_replace_rcu(&old->pid_links[type], &new->pid_links[type]);
 }
 
@@ -474,7 +492,7 @@ pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
 	struct upid *upid;
 	pid_t nr = 0;
 
-	if (pid && ns->level <= pid->level) {
+	if (pid && ns && ns->level <= pid->level) {
 		upid = &pid->numbers[ns->level];
 		if (upid->ns == ns)
 			nr = upid->nr;
@@ -497,7 +515,8 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
 	rcu_read_lock();
 	if (!ns)
 		ns = task_active_pid_ns(current);
-	nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
+	if (ns)
+		nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
 	rcu_read_unlock();
 
 	return nr;
@@ -519,23 +538,21 @@ struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
 {
 	return idr_get_next(&ns->idr, &nr);
 }
+EXPORT_SYMBOL_GPL(find_ge_pid);
 
 struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags)
 {
-	struct fd f;
+	CLASS(fd, f)(fd);
 	struct pid *pid;
 
-	f = fdget(fd);
-	if (!f.file)
+	if (fd_empty(f))
 		return ERR_PTR(-EBADF);
 
-	pid = pidfd_pid(f.file);
+	pid = pidfd_pid(fd_file(f));
 	if (!IS_ERR(pid)) {
 		get_pid(pid);
-		*flags = f.file->f_flags;
+		*flags = fd_file(f)->f_flags;
 	}
-
-	fdput(f);
 	return pid;
 }
 
@@ -548,25 +565,34 @@ struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags)
  * Return the task associated with @pidfd. The function takes a reference on
  * the returned task. The caller is responsible for releasing that reference.
  *
- * Currently, the process identified by @pidfd is always a thread-group leader.
- * This restriction currently exists for all aspects of pidfds including pidfd
- * creation (CLONE_PIDFD cannot be used with CLONE_THREAD) and pidfd polling
- * (only supports thread group leaders).
- *
  * Return: On success, the task_struct associated with the pidfd.
  *	   On error, a negative errno number will be returned.
  */
 struct task_struct *pidfd_get_task(int pidfd, unsigned int *flags)
 {
-	unsigned int f_flags;
+	unsigned int f_flags = 0;
 	struct pid *pid;
 	struct task_struct *task;
+	enum pid_type type;
 
-	pid = pidfd_get_pid(pidfd, &f_flags);
-	if (IS_ERR(pid))
-		return ERR_CAST(pid);
+	switch (pidfd) {
+	case  PIDFD_SELF_THREAD:
+		type = PIDTYPE_PID;
+		pid = get_task_pid(current, type);
+		break;
+	case  PIDFD_SELF_THREAD_GROUP:
+		type = PIDTYPE_TGID;
+		pid = get_task_pid(current, type);
+		break;
+	default:
+		pid = pidfd_get_pid(pidfd, &f_flags);
+		if (IS_ERR(pid))
+			return ERR_CAST(pid);
+		type = PIDTYPE_TGID;
+		break;
+	}
 
-	task = get_pid_task(pid, PIDTYPE_TGID);
+	task = get_pid_task(pid, type);
 	put_pid(pid);
 	if (!task)
 		return ERR_PTR(-ESRCH);
@@ -591,36 +617,28 @@ struct task_struct *pidfd_get_task(int pidfd, unsigned int *flags)
  * Return: On success, a cloexec pidfd is returned.
  *         On error, a negative errno number will be returned.
  */
-int pidfd_create(struct pid *pid, unsigned int flags)
+static int pidfd_create(struct pid *pid, unsigned int flags)
 {
-	int fd;
-
-	if (!pid || !pid_has_task(pid, PIDTYPE_TGID))
-		return -EINVAL;
-
-	if (flags & ~(O_NONBLOCK | O_RDWR | O_CLOEXEC))
-		return -EINVAL;
+	int pidfd;
+	struct file *pidfd_file;
 
-	fd = anon_inode_getfd("[pidfd]", &pidfd_fops, get_pid(pid),
-			      flags | O_RDWR | O_CLOEXEC);
-	if (fd < 0)
-		put_pid(pid);
+	pidfd = pidfd_prepare(pid, flags, &pidfd_file);
+	if (pidfd < 0)
+		return pidfd;
 
-	return fd;
+	fd_install(pidfd, pidfd_file);
+	return pidfd;
 }
 
 /**
- * pidfd_open() - Open new pid file descriptor.
+ * sys_pidfd_open() - Open new pid file descriptor.
  *
  * @pid:   pid for which to retrieve a pidfd
  * @flags: flags to pass
  *
  * This creates a new pid file descriptor with the O_CLOEXEC flag set for
- * the process identified by @pid. Currently, the process identified by
- * @pid must be a thread-group leader. This restriction currently exists
- * for all aspects of pidfds including pidfd creation (CLONE_PIDFD cannot
- * be used with CLONE_THREAD) and pidfd polling (only supports thread group
- * leaders).
+ * the task identified by @pid. Without PIDFD_THREAD flag the target task
+ * must be a thread-group leader.
  *
  * Return: On success, a cloexec pidfd is returned.
  *         On error, a negative errno number will be returned.
@@ -630,7 +648,7 @@ SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
 	int fd;
 	struct pid *p;
 
-	if (flags & ~PIDFD_NONBLOCK)
+	if (flags & ~(PIDFD_NONBLOCK | PIDFD_THREAD))
 		return -EINVAL;
 
 	if (pid <= 0)
@@ -646,23 +664,168 @@ SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
 	return fd;
 }
 
+#ifdef CONFIG_SYSCTL
+static struct ctl_table_set *pid_table_root_lookup(struct ctl_table_root *root)
+{
+	return &task_active_pid_ns(current)->set;
+}
+
+static int set_is_seen(struct ctl_table_set *set)
+{
+	return &task_active_pid_ns(current)->set == set;
+}
+
+static int pid_table_root_permissions(struct ctl_table_header *head,
+				      const struct ctl_table *table)
+{
+	struct pid_namespace *pidns =
+		container_of(head->set, struct pid_namespace, set);
+	int mode = table->mode;
+
+	if (ns_capable_noaudit(pidns->user_ns, CAP_SYS_ADMIN) ||
+	    uid_eq(current_euid(), make_kuid(pidns->user_ns, 0)))
+		mode = (mode & S_IRWXU) >> 6;
+	else if (in_egroup_p(make_kgid(pidns->user_ns, 0)))
+		mode = (mode & S_IRWXG) >> 3;
+	else
+		mode = mode & S_IROTH;
+	return (mode << 6) | (mode << 3) | mode;
+}
+
+static void pid_table_root_set_ownership(struct ctl_table_header *head,
+					 kuid_t *uid, kgid_t *gid)
+{
+	struct pid_namespace *pidns =
+		container_of(head->set, struct pid_namespace, set);
+	kuid_t ns_root_uid;
+	kgid_t ns_root_gid;
+
+	ns_root_uid = make_kuid(pidns->user_ns, 0);
+	if (uid_valid(ns_root_uid))
+		*uid = ns_root_uid;
+
+	ns_root_gid = make_kgid(pidns->user_ns, 0);
+	if (gid_valid(ns_root_gid))
+		*gid = ns_root_gid;
+}
+
+static struct ctl_table_root pid_table_root = {
+	.lookup		= pid_table_root_lookup,
+	.permissions	= pid_table_root_permissions,
+	.set_ownership	= pid_table_root_set_ownership,
+};
+
+static int proc_do_cad_pid(const struct ctl_table *table, int write, void *buffer,
+		size_t *lenp, loff_t *ppos)
+{
+	struct pid *new_pid;
+	pid_t tmp_pid;
+	int r;
+	struct ctl_table tmp_table = *table;
+
+	tmp_pid = pid_vnr(cad_pid);
+	tmp_table.data = &tmp_pid;
+
+	r = proc_dointvec(&tmp_table, write, buffer, lenp, ppos);
+	if (r || !write)
+		return r;
+
+	new_pid = find_get_pid(tmp_pid);
+	if (!new_pid)
+		return -ESRCH;
+
+	put_pid(xchg(&cad_pid, new_pid));
+	return 0;
+}
+
+static const struct ctl_table pid_table[] = {
+	{
+		.procname	= "pid_max",
+		.data		= &init_pid_ns.pid_max,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &pid_max_min,
+		.extra2		= &pid_max_max,
+	},
+#ifdef CONFIG_PROC_SYSCTL
+	{
+		.procname	= "cad_pid",
+		.maxlen		= sizeof(int),
+		.mode		= 0600,
+		.proc_handler	= proc_do_cad_pid,
+	},
+#endif
+};
+#endif
+
+int register_pidns_sysctls(struct pid_namespace *pidns)
+{
+#ifdef CONFIG_SYSCTL
+	struct ctl_table *tbl;
+
+	setup_sysctl_set(&pidns->set, &pid_table_root, set_is_seen);
+
+	tbl = kmemdup(pid_table, sizeof(pid_table), GFP_KERNEL);
+	if (!tbl)
+		return -ENOMEM;
+	tbl->data = &pidns->pid_max;
+	pidns->pid_max = min(pid_max_max, max_t(int, pidns->pid_max,
+			     PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
+
+	pidns->sysctls = __register_sysctl_table(&pidns->set, "kernel", tbl,
+						 ARRAY_SIZE(pid_table));
+	if (!pidns->sysctls) {
+		kfree(tbl);
+		retire_sysctl_set(&pidns->set);
+		return -ENOMEM;
+	}
+#endif
+	return 0;
+}
+
+void unregister_pidns_sysctls(struct pid_namespace *pidns)
+{
+#ifdef CONFIG_SYSCTL
+	const struct ctl_table *tbl;
+
+	tbl = pidns->sysctls->ctl_table_arg;
+	unregister_sysctl_table(pidns->sysctls);
+	retire_sysctl_set(&pidns->set);
+	kfree(tbl);
+#endif
+}
+
 void __init pid_idr_init(void)
 {
 	/* Verify no one has done anything silly: */
 	BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_ADDING);
 
 	/* bump default and minimum pid_max based on number of cpus */
-	pid_max = min(pid_max_max, max_t(int, pid_max,
-				PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
+	init_pid_ns.pid_max = min(pid_max_max, max_t(int, init_pid_ns.pid_max,
+				  PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
 	pid_max_min = max_t(int, pid_max_min,
 				PIDS_PER_CPU_MIN * num_possible_cpus());
-	pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
+	pr_info("pid_max: default: %u minimum: %u\n", init_pid_ns.pid_max, pid_max_min);
 
 	idr_init(&init_pid_ns.idr);
 
-	init_pid_ns.pid_cachep = KMEM_CACHE(pid,
-			SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT);
+	init_pid_ns.pid_cachep = kmem_cache_create("pid",
+			struct_size_t(struct pid, numbers, 1),
+			__alignof__(struct pid),
+			SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT,
+			NULL);
+}
+
+static __init int pid_namespace_sysctl_init(void)
+{
+#ifdef CONFIG_SYSCTL
+	/* "kernel" directory will have already been initialized. */
+	BUG_ON(register_pidns_sysctls(&init_pid_ns));
+#endif
+	return 0;
 }
+subsys_initcall(pid_namespace_sysctl_init);
 
 static struct file *__pidfd_fget(struct task_struct *task, int fd)
 {
@@ -680,7 +843,26 @@ static struct file *__pidfd_fget(struct task_struct *task, int fd)
 
 	up_read(&task->signal->exec_update_lock);
 
-	return file ?: ERR_PTR(-EBADF);
+	if (!file) {
+		/*
+		 * It is possible that the target thread is exiting; it can be
+		 * either:
+		 * 1. before exit_signals(), which gives a real fd
+		 * 2. before exit_files() takes the task_lock() gives a real fd
+		 * 3. after exit_files() releases task_lock(), ->files is NULL;
+		 *    this has PF_EXITING, since it was set in exit_signals(),
+		 *    __pidfd_fget() returns EBADF.
+		 * In case 3 we get EBADF, but that really means ESRCH, since
+		 * the task is currently exiting and has freed its files
+		 * struct, so we fix it up.
+		 */
+		if (task->flags & PF_EXITING)
+			file = ERR_PTR(-ESRCH);
+		else
+			file = ERR_PTR(-EBADF);
+	}
+
+	return file;
 }
 
 static int pidfd_getfd(struct pid *pid, int fd)
@@ -698,7 +880,7 @@ static int pidfd_getfd(struct pid *pid, int fd)
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 
-	ret = receive_fd(file, O_CLOEXEC);
+	ret = receive_fd(file, NULL, O_CLOEXEC);
 	fput(file);
 
 	return ret;
@@ -724,23 +906,18 @@ SYSCALL_DEFINE3(pidfd_getfd, int, pidfd, int, fd,
 		unsigned int, flags)
 {
 	struct pid *pid;
-	struct fd f;
-	int ret;
 
 	/* flags is currently unused - make sure it's unset */
 	if (flags)
 		return -EINVAL;
 
-	f = fdget(pidfd);
-	if (!f.file)
+	CLASS(fd, f)(pidfd);
+	if (fd_empty(f))
 		return -EBADF;
 
-	pid = pidfd_pid(f.file);
+	pid = pidfd_pid(fd_file(f));
 	if (IS_ERR(pid))
-		ret = PTR_ERR(pid);
-	else
-		ret = pidfd_getfd(pid, fd);
+		return PTR_ERR(pid);
 
-	fdput(f);
-	return ret;
+	return pidfd_getfd(pid, fd);
 }