Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 582 insertions, 0 deletions

diff --git a/drivers/tty/tty_jobctrl.c b/drivers/tty/tty_jobctrl.c
new file mode 100644
index 000000000..37929fb56
--- /dev/null
+++ b/drivers/tty/tty_jobctrl.c
@@ -0,0 +1,582 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/tty.h>
+#include <linux/fcntl.h>
+#include <linux/uaccess.h>
+#include "tty.h"
+
+static int is_ignored(int sig)
+{
+	return (sigismember(&current->blocked, sig) ||
+		current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
+}
+
+/**
+ *	__tty_check_change	-	check for POSIX terminal changes
+ *	@tty: tty to check
+ *	@sig: signal to send
+ *
+ *	If we try to write to, or set the state of, a terminal and we're
+ *	not in the foreground, send a SIGTTOU.  If the signal is blocked or
+ *	ignored, go ahead and perform the operation.  (POSIX 7.2)
+ *
+ *	Locking: ctrl.lock
+ */
+int __tty_check_change(struct tty_struct *tty, int sig)
+{
+	unsigned long flags;
+	struct pid *pgrp, *tty_pgrp;
+	int ret = 0;
+
+	if (current->signal->tty != tty)
+		return 0;
+
+	rcu_read_lock();
+	pgrp = task_pgrp(current);
+
+	spin_lock_irqsave(&tty->ctrl.lock, flags);
+	tty_pgrp = tty->ctrl.pgrp;
+	spin_unlock_irqrestore(&tty->ctrl.lock, flags);
+
+	if (tty_pgrp && pgrp != tty_pgrp) {
+		if (is_ignored(sig)) {
+			if (sig == SIGTTIN)
+				ret = -EIO;
+		} else if (is_current_pgrp_orphaned())
+			ret = -EIO;
+		else {
+			kill_pgrp(pgrp, sig, 1);
+			set_thread_flag(TIF_SIGPENDING);
+			ret = -ERESTARTSYS;
+		}
+	}
+	rcu_read_unlock();
+
+	if (!tty_pgrp)
+		tty_warn(tty, "sig=%d, tty->pgrp == NULL!\n", sig);
+
+	return ret;
+}
+
+int tty_check_change(struct tty_struct *tty)
+{
+	return __tty_check_change(tty, SIGTTOU);
+}
+EXPORT_SYMBOL(tty_check_change);
+
+void proc_clear_tty(struct task_struct *p)
+{
+	unsigned long flags;
+	struct tty_struct *tty;
+
+	spin_lock_irqsave(&p->sighand->siglock, flags);
+	tty = p->signal->tty;
+	p->signal->tty = NULL;
+	spin_unlock_irqrestore(&p->sighand->siglock, flags);
+	tty_kref_put(tty);
+}
+
+/**
+ * __proc_set_tty -  set the controlling terminal
+ *	@tty: tty structure
+ *
+ * Only callable by the session leader and only if it does not already have
+ * a controlling terminal.
+ *
+ * Caller must hold:  tty_lock()
+ *		      a readlock on tasklist_lock
+ *		      sighand lock
+ */
+static void __proc_set_tty(struct tty_struct *tty)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&tty->ctrl.lock, flags);
+	/*
+	 * The session and fg pgrp references will be non-NULL if
+	 * tiocsctty() is stealing the controlling tty
+	 */
+	put_pid(tty->ctrl.session);
+	put_pid(tty->ctrl.pgrp);
+	tty->ctrl.pgrp = get_pid(task_pgrp(current));
+	tty->ctrl.session = get_pid(task_session(current));
+	spin_unlock_irqrestore(&tty->ctrl.lock, flags);
+	if (current->signal->tty) {
+		tty_debug(tty, "current tty %s not NULL!!\n",
+			  current->signal->tty->name);
+		tty_kref_put(current->signal->tty);
+	}
+	put_pid(current->signal->tty_old_pgrp);
+	current->signal->tty = tty_kref_get(tty);
+	current->signal->tty_old_pgrp = NULL;
+}
+
+static void proc_set_tty(struct tty_struct *tty)
+{
+	spin_lock_irq(&current->sighand->siglock);
+	__proc_set_tty(tty);
+	spin_unlock_irq(&current->sighand->siglock);
+}
+
+/*
+ * Called by tty_open() to set the controlling tty if applicable.
+ */
+void tty_open_proc_set_tty(struct file *filp, struct tty_struct *tty)
+{
+	read_lock(&tasklist_lock);
+	spin_lock_irq(&current->sighand->siglock);
+	if (current->signal->leader &&
+	    !current->signal->tty &&
+	    tty->ctrl.session == NULL) {
+		/*
+		 * Don't let a process that only has write access to the tty
+		 * obtain the privileges associated with having a tty as
+		 * controlling terminal (being able to reopen it with full
+		 * access through /dev/tty, being able to perform pushback).
+		 * Many distributions set the group of all ttys to "tty" and
+		 * grant write-only access to all terminals for setgid tty
+		 * binaries, which should not imply full privileges on all ttys.
+		 *
+		 * This could theoretically break old code that performs open()
+		 * on a write-only file descriptor. In that case, it might be
+		 * necessary to also permit this if
+		 * inode_permission(inode, MAY_READ) == 0.
+		 */
+		if (filp->f_mode & FMODE_READ)
+			__proc_set_tty(tty);
+	}
+	spin_unlock_irq(&current->sighand->siglock);
+	read_unlock(&tasklist_lock);
+}
+
+struct tty_struct *get_current_tty(void)
+{
+	struct tty_struct *tty;
+	unsigned long flags;
+
+	spin_lock_irqsave(&current->sighand->siglock, flags);
+	tty = tty_kref_get(current->signal->tty);
+	spin_unlock_irqrestore(&current->sighand->siglock, flags);
+	return tty;
+}
+EXPORT_SYMBOL_GPL(get_current_tty);
+
+/*
+ * Called from tty_release().
+ */
+void session_clear_tty(struct pid *session)
+{
+	struct task_struct *p;
+
+	do_each_pid_task(session, PIDTYPE_SID, p) {
+		proc_clear_tty(p);
+	} while_each_pid_task(session, PIDTYPE_SID, p);
+}
+
+/**
+ *	tty_signal_session_leader	- sends SIGHUP to session leader
+ *	@tty: controlling tty
+ *	@exit_session: if non-zero, signal all foreground group processes
+ *
+ *	Send SIGHUP and SIGCONT to the session leader and its process group.
+ *	Optionally, signal all processes in the foreground process group.
+ *
+ *	Returns the number of processes in the session with this tty
+ *	as their controlling terminal. This value is used to drop
+ *	tty references for those processes.
+ */
+int tty_signal_session_leader(struct tty_struct *tty, int exit_session)
+{
+	struct task_struct *p;
+	int refs = 0;
+	struct pid *tty_pgrp = NULL;
+
+	read_lock(&tasklist_lock);
+	if (tty->ctrl.session) {
+		do_each_pid_task(tty->ctrl.session, PIDTYPE_SID, p) {
+			spin_lock_irq(&p->sighand->siglock);
+			if (p->signal->tty == tty) {
+				p->signal->tty = NULL;
+				/*
+				 * We defer the dereferences outside of
+				 * the tasklist lock.
+				 */
+				refs++;
+			}
+			if (!p->signal->leader) {
+				spin_unlock_irq(&p->sighand->siglock);
+				continue;
+			}
+			send_signal_locked(SIGHUP, SEND_SIG_PRIV, p, PIDTYPE_TGID);
+			send_signal_locked(SIGCONT, SEND_SIG_PRIV, p, PIDTYPE_TGID);
+			put_pid(p->signal->tty_old_pgrp);  /* A noop */
+			spin_lock(&tty->ctrl.lock);
+			tty_pgrp = get_pid(tty->ctrl.pgrp);
+			if (tty->ctrl.pgrp)
+				p->signal->tty_old_pgrp =
+					get_pid(tty->ctrl.pgrp);
+			spin_unlock(&tty->ctrl.lock);
+			spin_unlock_irq(&p->sighand->siglock);
+		} while_each_pid_task(tty->ctrl.session, PIDTYPE_SID, p);
+	}
+	read_unlock(&tasklist_lock);
+
+	if (tty_pgrp) {
+		if (exit_session)
+			kill_pgrp(tty_pgrp, SIGHUP, exit_session);
+		put_pid(tty_pgrp);
+	}
+
+	return refs;
+}
+
+/**
+ *	disassociate_ctty	-	disconnect controlling tty
+ *	@on_exit: true if exiting so need to "hang up" the session
+ *
+ *	This function is typically called only by the session leader, when
+ *	it wants to disassociate itself from its controlling tty.
+ *
+ *	It performs the following functions:
+ *	(1)  Sends a SIGHUP and SIGCONT to the foreground process group
+ *	(2)  Clears the tty from being controlling the session
+ *	(3)  Clears the controlling tty for all processes in the
+ *		session group.
+ *
+ *	The argument on_exit is set to 1 if called when a process is
+ *	exiting; it is 0 if called by the ioctl TIOCNOTTY.
+ *
+ *	Locking:
+ *		BTM is taken for hysterical raisons, and held when
+ *		  called from no_tty().
+ *		  tty_mutex is taken to protect tty
+ *		  ->siglock is taken to protect ->signal/->sighand
+ *		  tasklist_lock is taken to walk process list for sessions
+ *		    ->siglock is taken to protect ->signal/->sighand
+ */
+void disassociate_ctty(int on_exit)
+{
+	struct tty_struct *tty;
+
+	if (!current->signal->leader)
+		return;
+
+	tty = get_current_tty();
+	if (tty) {
+		if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY) {
+			tty_vhangup_session(tty);
+		} else {
+			struct pid *tty_pgrp = tty_get_pgrp(tty);
+
+			if (tty_pgrp) {
+				kill_pgrp(tty_pgrp, SIGHUP, on_exit);
+				if (!on_exit)
+					kill_pgrp(tty_pgrp, SIGCONT, on_exit);
+				put_pid(tty_pgrp);
+			}
+		}
+		tty_kref_put(tty);
+
+	} else if (on_exit) {
+		struct pid *old_pgrp;
+
+		spin_lock_irq(&current->sighand->siglock);
+		old_pgrp = current->signal->tty_old_pgrp;
+		current->signal->tty_old_pgrp = NULL;
+		spin_unlock_irq(&current->sighand->siglock);
+		if (old_pgrp) {
+			kill_pgrp(old_pgrp, SIGHUP, on_exit);
+			kill_pgrp(old_pgrp, SIGCONT, on_exit);
+			put_pid(old_pgrp);
+		}
+		return;
+	}
+
+	tty = get_current_tty();
+	if (tty) {
+		unsigned long flags;
+
+		tty_lock(tty);
+		spin_lock_irqsave(&tty->ctrl.lock, flags);
+		put_pid(tty->ctrl.session);
+		put_pid(tty->ctrl.pgrp);
+		tty->ctrl.session = NULL;
+		tty->ctrl.pgrp = NULL;
+		spin_unlock_irqrestore(&tty->ctrl.lock, flags);
+		tty_unlock(tty);
+		tty_kref_put(tty);
+	}
+
+	/* If tty->ctrl.pgrp is not NULL, it may be assigned to
+	 * current->signal->tty_old_pgrp in a race condition, and
+	 * cause pid memleak. Release current->signal->tty_old_pgrp
+	 * after tty->ctrl.pgrp set to NULL.
+	 */
+	spin_lock_irq(&current->sighand->siglock);
+	put_pid(current->signal->tty_old_pgrp);
+	current->signal->tty_old_pgrp = NULL;
+	spin_unlock_irq(&current->sighand->siglock);
+
+	/* Now clear signal->tty under the lock */
+	read_lock(&tasklist_lock);
+	session_clear_tty(task_session(current));
+	read_unlock(&tasklist_lock);
+}
+
+/*
+ *
+ *	no_tty	- Ensure the current process does not have a controlling tty
+ */
+void no_tty(void)
+{
+	/*
+	 * FIXME: Review locking here. The tty_lock never covered any race
+	 * between a new association and proc_clear_tty but possibly we need
+	 * to protect against this anyway.
+	 */
+	struct task_struct *tsk = current;
+
+	disassociate_ctty(0);
+	proc_clear_tty(tsk);
+}
+
+/**
+ *	tiocsctty	-	set controlling tty
+ *	@tty: tty structure
+ *	@file: file structure used to check permissions
+ *	@arg: user argument
+ *
+ *	This ioctl is used to manage job control. It permits a session
+ *	leader to set this tty as the controlling tty for the session.
+ *
+ *	Locking:
+ *		Takes tty_lock() to serialize proc_set_tty() for this tty
+ *		Takes tasklist_lock internally to walk sessions
+ *		Takes ->siglock() when updating signal->tty
+ */
+static int tiocsctty(struct tty_struct *tty, struct file *file, int arg)
+{
+	int ret = 0;
+
+	tty_lock(tty);
+	read_lock(&tasklist_lock);
+
+	if (current->signal->leader &&
+			task_session(current) == tty->ctrl.session)
+		goto unlock;
+
+	/*
+	 * The process must be a session leader and
+	 * not have a controlling tty already.
+	 */
+	if (!current->signal->leader || current->signal->tty) {
+		ret = -EPERM;
+		goto unlock;
+	}
+
+	if (tty->ctrl.session) {
+		/*
+		 * This tty is already the controlling
+		 * tty for another session group!
+		 */
+		if (arg == 1 && capable(CAP_SYS_ADMIN)) {
+			/*
+			 * Steal it away
+			 */
+			session_clear_tty(tty->ctrl.session);
+		} else {
+			ret = -EPERM;
+			goto unlock;
+		}
+	}
+
+	/* See the comment in tty_open_proc_set_tty(). */
+	if ((file->f_mode & FMODE_READ) == 0 && !capable(CAP_SYS_ADMIN)) {
+		ret = -EPERM;
+		goto unlock;
+	}
+
+	proc_set_tty(tty);
+unlock:
+	read_unlock(&tasklist_lock);
+	tty_unlock(tty);
+	return ret;
+}
+
+/**
+ *	tty_get_pgrp	-	return a ref counted pgrp pid
+ *	@tty: tty to read
+ *
+ *	Returns a refcounted instance of the pid struct for the process
+ *	group controlling the tty.
+ */
+struct pid *tty_get_pgrp(struct tty_struct *tty)
+{
+	unsigned long flags;
+	struct pid *pgrp;
+
+	spin_lock_irqsave(&tty->ctrl.lock, flags);
+	pgrp = get_pid(tty->ctrl.pgrp);
+	spin_unlock_irqrestore(&tty->ctrl.lock, flags);
+
+	return pgrp;
+}
+EXPORT_SYMBOL_GPL(tty_get_pgrp);
+
+/*
+ * This checks not only the pgrp, but falls back on the pid if no
+ * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
+ * without this...
+ *
+ * The caller must hold rcu lock or the tasklist lock.
+ */
+static struct pid *session_of_pgrp(struct pid *pgrp)
+{
+	struct task_struct *p;
+	struct pid *sid = NULL;
+
+	p = pid_task(pgrp, PIDTYPE_PGID);
+	if (p == NULL)
+		p = pid_task(pgrp, PIDTYPE_PID);
+	if (p != NULL)
+		sid = task_session(p);
+
+	return sid;
+}
+
+/**
+ *	tiocgpgrp		-	get process group
+ *	@tty: tty passed by user
+ *	@real_tty: tty side of the tty passed by the user if a pty else the tty
+ *	@p: returned pid
+ *
+ *	Obtain the process group of the tty. If there is no process group
+ *	return an error.
+ *
+ *	Locking: none. Reference to current->signal->tty is safe.
+ */
+static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
+{
+	struct pid *pid;
+	int ret;
+	/*
+	 * (tty == real_tty) is a cheap way of
+	 * testing if the tty is NOT a master pty.
+	 */
+	if (tty == real_tty && current->signal->tty != real_tty)
+		return -ENOTTY;
+	pid = tty_get_pgrp(real_tty);
+	ret =  put_user(pid_vnr(pid), p);
+	put_pid(pid);
+	return ret;
+}
+
+/**
+ *	tiocspgrp		-	attempt to set process group
+ *	@tty: tty passed by user
+ *	@real_tty: tty side device matching tty passed by user
+ *	@p: pid pointer
+ *
+ *	Set the process group of the tty to the session passed. Only
+ *	permitted where the tty session is our session.
+ *
+ *	Locking: RCU, ctrl lock
+ */
+static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
+{
+	struct pid *pgrp;
+	pid_t pgrp_nr;
+	int retval = tty_check_change(real_tty);
+
+	if (retval == -EIO)
+		return -ENOTTY;
+	if (retval)
+		return retval;
+
+	if (get_user(pgrp_nr, p))
+		return -EFAULT;
+	if (pgrp_nr < 0)
+		return -EINVAL;
+
+	guard(spinlock_irq)(&real_tty->ctrl.lock);
+	if (!current->signal->tty ||
+	    (current->signal->tty != real_tty) ||
+	    (real_tty->ctrl.session != task_session(current)))
+		return -ENOTTY;
+
+	guard(rcu)();
+	pgrp = find_vpid(pgrp_nr);
+	if (!pgrp)
+		return -ESRCH;
+	if (session_of_pgrp(pgrp) != task_session(current))
+		return -EPERM;
+
+	put_pid(real_tty->ctrl.pgrp);
+	real_tty->ctrl.pgrp = get_pid(pgrp);
+
+	return 0;
+}
+
+/**
+ *	tiocgsid		-	get session id
+ *	@tty: tty passed by user
+ *	@real_tty: tty side of the tty passed by the user if a pty else the tty
+ *	@p: pointer to returned session id
+ *
+ *	Obtain the session id of the tty. If there is no session
+ *	return an error.
+ */
+static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
+{
+	pid_t sid;
+
+	/*
+	 * (tty == real_tty) is a cheap way of
+	 * testing if the tty is NOT a master pty.
+	 */
+	if (tty == real_tty && current->signal->tty != real_tty)
+		return -ENOTTY;
+
+	scoped_guard(spinlock_irqsave, &real_tty->ctrl.lock) {
+		if (!real_tty->ctrl.session)
+			return -ENOTTY;
+		sid = pid_vnr(real_tty->ctrl.session);
+	}
+
+	return put_user(sid, p);
+}
+
+/*
+ * Called from tty_ioctl(). If tty is a pty then real_tty is the slave side,
+ * if not then tty == real_tty.
+ */
+long tty_jobctrl_ioctl(struct tty_struct *tty, struct tty_struct *real_tty,
+		       struct file *file, unsigned int cmd, unsigned long arg)
+{
+	void __user *p = (void __user *)arg;
+
+	switch (cmd) {
+	case TIOCNOTTY:
+		if (current->signal->tty != tty)
+			return -ENOTTY;
+		no_tty();
+		return 0;
+	case TIOCSCTTY:
+		return tiocsctty(real_tty, file, arg);
+	case TIOCGPGRP:
+		return tiocgpgrp(tty, real_tty, p);
+	case TIOCSPGRP:
+		return tiocspgrp(tty, real_tty, p);
+	case TIOCGSID:
+		return tiocgsid(tty, real_tty, p);
+	}
+	return -ENOIOCTLCMD;
+}