Merge v7.1.5linux-rolling-stable

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

7 files changed, 150 insertions, 86 deletions

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 6e173d70d825..c9aac73ba97a 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -512,8 +512,6 @@ static enum alarmtimer_type clock2alarm(clockid_t clockid)
  * @now: time at the timer expiration
  *
  * Posix timer callback for expired alarm timers.
- *
- * Return: whether the timer is to be restarted
  */
 static void alarm_handle_timer(struct alarm *alarm, ktime_t now)
 {
@@ -527,12 +525,13 @@ static void alarm_handle_timer(struct alarm *alarm, ktime_t now)
  * alarm_timer_rearm - Posix timer callback for rearming timer
  * @timr:	Pointer to the posixtimer data struct
  */
-static void alarm_timer_rearm(struct k_itimer *timr)
+static bool alarm_timer_rearm(struct k_itimer *timr)
 {
 	struct alarm *alarm = &timr->it.alarm.alarmtimer;
 
 	timr->it_overrun += alarm_forward_now(alarm, timr->it_interval);
 	alarm_start(alarm, alarm->node.expires);
+	return true;
 }
 
 /**
@@ -588,7 +587,7 @@ static void alarm_timer_wait_running(struct k_itimer *timr)
  * @absolute:	Expiry value is absolute time
  * @sigev_none:	Posix timer does not deliver signals
  */
-static void alarm_timer_arm(struct k_itimer *timr, ktime_t expires,
+static bool alarm_timer_arm(struct k_itimer *timr, ktime_t expires,
 			    bool absolute, bool sigev_none)
 {
 	struct alarm *alarm = &timr->it.alarm.alarmtimer;
@@ -600,6 +599,7 @@ static void alarm_timer_arm(struct k_itimer *timr, ktime_t expires,
 		alarm->node.expires = expires;
 	else
 		alarm_start(&timr->it.alarm.alarmtimer, expires);
+	return true;
 }
 
 /**
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 6f3ddb2b1f46..a7d3e8229c4b 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -19,7 +19,7 @@
 
 #include "posix-timers.h"
 
-static void posix_cpu_timer_rearm(struct k_itimer *timer);
+static bool posix_cpu_timer_rearm(struct k_itimer *timer);
 
 void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
 {
@@ -41,7 +41,7 @@ void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
  */
 int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
 {
-	u64 nsecs = rlim_new * NSEC_PER_SEC;
+	u64 nsecs = (u64)rlim_new * NSEC_PER_SEC;
 	unsigned long irq_fl;
 
 	if (!lock_task_sighand(task, &irq_fl))
@@ -461,6 +461,109 @@ static void disarm_timer(struct k_itimer *timer, struct task_struct *p)
 		trigger_base_recalc_expires(timer, p);
 }
 
+/*
+ * Lookup the task via timer->it.cpu.pid and attempt to lock the task's sighand.
+ *
+ * This can race with the reaping of the task:
+ *
+ * CPU0					CPU1
+ *
+ * // Finds task
+ * p = pid_task(pid, pid_type);		__exit_signal(p)
+ *					  lock(p, sighand);
+ *					  posix_cpu_timers*_exit();
+ * sighand = lock_task_sighand(p);	  unhash_task(p);
+ *					  p->sighand = NULL;
+ *					  unlock(sighand);
+ *
+ * In this case sighand is NULL, which means the task and the associated timer
+ * queue cannot be longer accessed safely.
+ *
+ * __exit_signal() invokes posix_cpu_timers_exit() and if the thread group is
+ * dead it also invokes posix_cpu_timers_group_exit(). These functions delete
+ * all pending timers from the related timer queues. The POSIX timers (k_itimer)
+ * themself are still accessible, but not longer connected to the task.
+ *
+ * exec() works slightly differently. The task which exec()'s terminates all
+ * other threads in the thread group and runs __exit_signal() on them. As the
+ * thread group is not dead they only clean up the per task timers via
+ * posix_cpu_timers_exit().
+ *
+ * As the TGID on exec() stays the same per process timers stay queued, if they
+ * are armed. This works without a problem when exec() is done by the thread
+ * group leader. If a non-leader thread exec()'s this can end up in the
+ * following scenario:
+ *
+ * CPU0					CPU1
+ * // Returns old leader
+ * p = pid_task(pid, pid_type);		de_thread()
+ *					switch_leader()
+ *					release_task(old leader)
+ *					  __exit_signal()
+ *					  old_leader->sighand = NULL;
+ * // Returns NULL
+ * sighand = lock_task_sighand(p)
+ *
+ * That's problematic for several functions:
+ *
+ *  - posix_cpu_timer_del(): If the timer is still enqueued on the task the
+ *    underlying k_itimer will be freed which results in a UAF in
+ *    run_posix_cpu_timers() or on timerqueue related add/delete operations.
+ *    If the timer is not enqueued, the failure is harmless
+ *
+ *  - posix_cpu_timer_set(): Independent of the enqueued state that results in a
+ *    transient failure which is user space visible (-ESRCH) for regular posix
+ *    timers. But for the use case in do_cpu_nanosleep() it's the same UAF
+ *    problem just that the timer is allocated on the stack.
+ *
+ *  - posix_cpu_timer_rearm(): Timer is not enqueued at that point, but this
+ *    silently ignores the rearm request, which is a functional problem as the
+ *    timer wont expire anymore.
+ */
+static struct task_struct *timer_lock_sighand(struct k_itimer *timer, unsigned long *flags)
+{
+	enum pid_type type = clock_pid_type(timer->it_clock);
+	struct cpu_timer *ctmr = &timer->it.cpu;
+
+	guard(rcu)();
+
+	for (;;) {
+		struct task_struct *t = pid_task(timer->it.cpu.pid, type);
+
+		/* Fail if the task cannot be found. */
+		if (!t)
+			break;
+
+		/* Try to lock the task's sighand */
+		if (lock_task_sighand(t, flags))
+			return t;
+
+		/*
+		 * The next PID lookup might either fail or return the new
+		 * leader. This is correct for both exit() and exec().
+		 */
+	}
+
+	/*
+	 * If the timer is still enqueued, warn. There is nothing safe to do
+	 * here as there might be two timers in there which are removed in
+	 * parallel and that will cause more damage than good. This should never
+	 * happen!
+	 *
+	 * Ensure that the stores to the timer and timerqueue are visible:
+	 *
+	 * __exit_signal()
+	 *   posix_cpu_timers*_exit()
+	 *   write_seqlock(seqlock)
+	 *	smp_wmb(); <-------
+	 *   __unhash_process()	  |	!pid_task()
+	 *			  ---->	smp_rmb();
+	 *				WARN_ON_ONCE(...)
+	 */
+	smp_rmb();
+	WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
+	return NULL;
+}
 
 /*
  * Clean up a CPU-clock timer that is about to be destroyed.
@@ -470,29 +573,13 @@ static void disarm_timer(struct k_itimer *timer, struct task_struct *p)
  */
 static int posix_cpu_timer_del(struct k_itimer *timer)
 {
-	struct cpu_timer *ctmr = &timer->it.cpu;
-	struct sighand_struct *sighand;
 	struct task_struct *p;
 	unsigned long flags;
 	int ret = 0;
 
-	rcu_read_lock();
-	p = cpu_timer_task_rcu(timer);
-	if (!p)
-		goto out;
+	p = timer_lock_sighand(timer, &flags);
 
-	/*
-	 * Protect against sighand release/switch in exit/exec and process/
-	 * thread timer list entry concurrent read/writes.
-	 */
-	sighand = lock_task_sighand(p, &flags);
-	if (unlikely(sighand == NULL)) {
-		/*
-		 * This raced with the reaping of the task. The exit cleanup
-		 * should have removed this timer from the timer queue.
-		 */
-		WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
-	} else {
+	if (likely(p)) {
 		if (timer->it.cpu.firing) {
 			/*
 			 * Prevent signal delivery. The timer cannot be dequeued
@@ -508,11 +595,8 @@ static int posix_cpu_timer_del(struct k_itimer *timer)
 		unlock_task_sighand(p, &flags);
 	}
 
-out:
-	rcu_read_unlock();
-
 	if (!ret) {
-		put_pid(ctmr->pid);
+		put_pid(timer->it.cpu.pid);
 		timer->it_status = POSIX_TIMER_DISARMED;
 	}
 	return ret;
@@ -626,21 +710,17 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
 	struct cpu_timer *ctmr = &timer->it.cpu;
 	u64 old_expires, new_expires, now;
-	struct sighand_struct *sighand;
 	struct task_struct *p;
 	unsigned long flags;
 	int ret = 0;
 
-	rcu_read_lock();
-	p = cpu_timer_task_rcu(timer);
-	if (!p) {
-		/*
-		 * If p has just been reaped, we can no
-		 * longer get any information about it at all.
-		 */
-		rcu_read_unlock();
+	p = timer_lock_sighand(timer, &flags);
+	/*
+	 * If p has just been reaped, we can no longer get any information about
+	 * it at all.
+	 */
+	if (!p)
 		return -ESRCH;
-	}
 
 	/*
 	 * Use the to_ktime conversion because that clamps the maximum
@@ -648,20 +728,6 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 	 */
 	new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
 
-	/*
-	 * Protect against sighand release/switch in exit/exec and p->cpu_timers
-	 * and p->signal->cpu_timers read/write in arm_timer()
-	 */
-	sighand = lock_task_sighand(p, &flags);
-	/*
-	 * If p has just been reaped, we can no
-	 * longer get any information about it at all.
-	 */
-	if (unlikely(sighand == NULL)) {
-		rcu_read_unlock();
-		return -ESRCH;
-	}
-
 	/* Retrieve the current expiry time before disarming the timer */
 	old_expires = cpu_timer_getexpires(ctmr);
 
@@ -698,7 +764,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 	/* Retry if the timer expiry is running concurrently */
 	if (unlikely(ret)) {
 		unlock_task_sighand(p, &flags);
-		goto out;
+		return ret;
 	}
 
 	/* Convert relative expiry time to absolute */
@@ -733,8 +799,6 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 	 */
 	if (!sigev_none && new_expires && now >= new_expires)
 		cpu_timer_fire(timer);
-out:
-	rcu_read_unlock();
 	return ret;
 }
 
@@ -1011,24 +1075,20 @@ static void check_process_timers(struct task_struct *tsk,
 /*
  * This is called from the signal code (via posixtimer_rearm)
  * when the last timer signal was delivered and we have to reload the timer.
+ *
+ * Return true unconditionally so the core code assumes the timer to be
+ * armed. Otherwise it would requeue the signal.
  */
-static void posix_cpu_timer_rearm(struct k_itimer *timer)
+static bool posix_cpu_timer_rearm(struct k_itimer *timer)
 {
 	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
 	struct task_struct *p;
-	struct sighand_struct *sighand;
 	unsigned long flags;
 	u64 now;
 
-	rcu_read_lock();
-	p = cpu_timer_task_rcu(timer);
-	if (!p)
-		goto out;
-
-	/* Protect timer list r/w in arm_timer() */
-	sighand = lock_task_sighand(p, &flags);
-	if (unlikely(sighand == NULL))
-		goto out;
+	p = timer_lock_sighand(timer, &flags);
+	if (unlikely(!p))
+		return true;
 
 	/*
 	 * Fetch the current sample and update the timer's expiry time.
@@ -1045,8 +1105,7 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer)
 	 */
 	arm_timer(timer, p);
 	unlock_task_sighand(p, &flags);
-out:
-	rcu_read_unlock();
+	return true;
 }
 
 /**
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 9331e1614124..da04ed42bf82 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -288,12 +288,13 @@ static inline int timer_overrun_to_int(struct k_itimer *timr)
 	return (int)timr->it_overrun_last;
 }
 
-static void common_hrtimer_rearm(struct k_itimer *timr)
+static bool common_hrtimer_rearm(struct k_itimer *timr)
 {
 	struct hrtimer *timer = &timr->it.real.timer;
 
 	timr->it_overrun += hrtimer_forward_now(timer, timr->it_interval);
 	hrtimer_restart(timer);
+	return true;
 }
 
 static bool __posixtimer_deliver_signal(struct kernel_siginfo *info, struct k_itimer *timr)
@@ -795,7 +796,7 @@ SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)
 		return timer_overrun_to_int(scoped_timer);
 }
 
-static void common_hrtimer_arm(struct k_itimer *timr, ktime_t expires,
+static bool common_hrtimer_arm(struct k_itimer *timr, ktime_t expires,
 			       bool absolute, bool sigev_none)
 {
 	struct hrtimer *timer = &timr->it.real.timer;
@@ -822,6 +823,7 @@ static void common_hrtimer_arm(struct k_itimer *timr, ktime_t expires,
 
 	if (!sigev_none)
 		hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
+	return true;
 }
 
 static int common_hrtimer_try_to_cancel(struct k_itimer *timr)
diff --git a/kernel/time/posix-timers.h b/kernel/time/posix-timers.h
index 7f259e845d24..4ea9611dd716 100644
--- a/kernel/time/posix-timers.h
+++ b/kernel/time/posix-timers.h
@@ -27,11 +27,11 @@ struct k_clock {
 	int	(*timer_del)(struct k_itimer *timr);
 	void	(*timer_get)(struct k_itimer *timr,
 			     struct itimerspec64 *cur_setting);
-	void	(*timer_rearm)(struct k_itimer *timr);
+	bool	(*timer_rearm)(struct k_itimer *timr);
 	s64	(*timer_forward)(struct k_itimer *timr, ktime_t now);
 	ktime_t	(*timer_remaining)(struct k_itimer *timr, ktime_t now);
 	int	(*timer_try_to_cancel)(struct k_itimer *timr);
-	void	(*timer_arm)(struct k_itimer *timr, ktime_t expires,
+	bool	(*timer_arm)(struct k_itimer *timr, ktime_t expires,
 			     bool absolute, bool sigev_none);
 	void	(*timer_wait_running)(struct k_itimer *timr);
 };
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index cbbb87a0c6e7..171393367b5c 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -797,15 +797,16 @@ static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime,
 		*last_update_time = ktime_to_us(now);
 
 	do {
+		ktime_t delta = 0;
+
 		seq = read_seqcount_begin(&ts->idle_sleeptime_seq);
 
 		if (tick_sched_flag_test(ts, TS_FLAG_IDLE_ACTIVE) && compute_delta) {
-			ktime_t delta = ktime_sub(now, ts->idle_entrytime);
-
-			idle = ktime_add(*sleeptime, delta);
-		} else {
-			idle = *sleeptime;
+			if (now > ts->idle_entrytime)
+				delta = ktime_sub(now, ts->idle_entrytime);
 		}
+
+		idle = ktime_add(*sleeptime, delta);
 	} while (read_seqcount_retry(&ts->idle_sleeptime_seq, seq));
 
 	return ktime_to_us(idle);
diff --git a/kernel/time/time.c b/kernel/time/time.c
index 771cef87ad3b..0dd63a91e7c5 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -251,7 +251,7 @@ COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
 		    get_user(new_ts.tv_nsec, &tv->tv_usec))
 			return -EFAULT;
 
-		if (new_ts.tv_nsec > USEC_PER_SEC || new_ts.tv_nsec < 0)
+		if (new_ts.tv_nsec >= USEC_PER_SEC || new_ts.tv_nsec < 0)
 			return -EINVAL;
 
 		new_ts.tv_nsec *= NSEC_PER_USEC;
diff --git a/kernel/time/timer_migration.h b/kernel/time/timer_migration.h
index 70879cde6fdd..4c0073f3d321 100644
--- a/kernel/time/timer_migration.h
+++ b/kernel/time/timer_migration.h
@@ -75,15 +75,17 @@ struct tmigr_group {
 /**
  * struct tmigr_cpu - timer migration per CPU group
  * @lock:		Lock protecting the tmigr_cpu group information
- * @online:		Indicates whether the CPU is online; In deactivate path
- *			it is required to know whether the migrator in the top
- *			level group is to be set offline, while a timer is
- *			pending. Then another online CPU needs to be notified to
- *			take over the migrator role. Furthermore the information
- *			is required in CPU hotplug path as the CPU is able to go
- *			idle before the timer migration hierarchy hotplug AP is
- *			reached. During this phase, the CPU has to handle the
+ * @available:		Indicates whether the CPU is available for handling
+ *			global timers. In the deactivate path it is required to
+ *			know whether the migrator in the top level group is to
+ *			be set offline, while a timer is pending. Then another
+ *			available CPU needs to be notified to take over the
+ *			migrator role. Furthermore the information is required
+ *			in the CPU hotplug path as the CPU is able to go idle
+ *			before the timer migration hierarchy hotplug callback is
+ *			reached.  During this phase, the CPU has to handle the
  *			global timers on its own and must not act as a migrator.
+
  * @idle:		Indicates whether the CPU is idle in the timer migration
  *			hierarchy
  * @remote:		Is set when timers of the CPU are expired remotely