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-rw-r--r--include/linux/posix-timers.h2
-rw-r--r--kernel/time/posix-cpu-timers.c73
2 files changed, 56 insertions, 19 deletions
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 3d10c84a97a9..e3f0f8585da4 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -69,7 +69,7 @@ static inline int clockid_to_fd(const clockid_t clk)
struct cpu_timer {
struct timerqueue_node node;
struct timerqueue_head *head;
- struct task_struct *task;
+ struct pid *pid;
struct list_head elist;
int firing;
};
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index ef936c5a910b..6df468a622fe 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -118,6 +118,16 @@ static inline int validate_clock_permissions(const clockid_t clock)
return __get_task_for_clock(clock, false, false) ? 0 : -EINVAL;
}
+static inline enum pid_type cpu_timer_pid_type(struct k_itimer *timer)
+{
+ return CPUCLOCK_PERTHREAD(timer->it_clock) ? PIDTYPE_PID : PIDTYPE_TGID;
+}
+
+static inline struct task_struct *cpu_timer_task_rcu(struct k_itimer *timer)
+{
+ return pid_task(timer->it.cpu.pid, cpu_timer_pid_type(timer));
+}
+
/*
* Update expiry time from increment, and increase overrun count,
* given the current clock sample.
@@ -391,7 +401,12 @@ static int posix_cpu_timer_create(struct k_itimer *new_timer)
new_timer->kclock = &clock_posix_cpu;
timerqueue_init(&new_timer->it.cpu.node);
- new_timer->it.cpu.task = p;
+ new_timer->it.cpu.pid = get_task_pid(p, cpu_timer_pid_type(new_timer));
+ /*
+ * get_task_for_clock() took a reference on @p. Drop it as the timer
+ * holds a reference on the pid of @p.
+ */
+ put_task_struct(p);
return 0;
}
@@ -404,13 +419,15 @@ static int posix_cpu_timer_create(struct k_itimer *new_timer)
static int posix_cpu_timer_del(struct k_itimer *timer)
{
struct cpu_timer *ctmr = &timer->it.cpu;
- struct task_struct *p = ctmr->task;
struct sighand_struct *sighand;
+ struct task_struct *p;
unsigned long flags;
int ret = 0;
- if (WARN_ON_ONCE(!p))
- return -EINVAL;
+ rcu_read_lock();
+ p = cpu_timer_task_rcu(timer);
+ if (!p)
+ goto out;
/*
* Protect against sighand release/switch in exit/exec and process/
@@ -432,8 +449,10 @@ static int posix_cpu_timer_del(struct k_itimer *timer)
unlock_task_sighand(p, &flags);
}
+out:
+ rcu_read_unlock();
if (!ret)
- put_task_struct(p);
+ put_pid(ctmr->pid);
return ret;
}
@@ -561,13 +580,21 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
u64 old_expires, new_expires, old_incr, val;
struct cpu_timer *ctmr = &timer->it.cpu;
- struct task_struct *p = ctmr->task;
struct sighand_struct *sighand;
+ struct task_struct *p;
unsigned long flags;
int ret = 0;
- if (WARN_ON_ONCE(!p))
- return -EINVAL;
+ 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();
+ return -ESRCH;
+ }
/*
* Use the to_ktime conversion because that clamps the maximum
@@ -584,8 +611,10 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
* If p has just been reaped, we can no
* longer get any information about it at all.
*/
- if (unlikely(sighand == NULL))
+ if (unlikely(sighand == NULL)) {
+ rcu_read_unlock();
return -ESRCH;
+ }
/*
* Disarm any old timer after extracting its expiry time.
@@ -690,6 +719,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
ret = 0;
out:
+ rcu_read_unlock();
if (old)
old->it_interval = ns_to_timespec64(old_incr);
@@ -701,10 +731,12 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp
clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
struct cpu_timer *ctmr = &timer->it.cpu;
u64 now, expires = cpu_timer_getexpires(ctmr);
- struct task_struct *p = ctmr->task;
+ struct task_struct *p;
- if (WARN_ON_ONCE(!p))
- return;
+ rcu_read_lock();
+ p = cpu_timer_task_rcu(timer);
+ if (!p)
+ goto out;
/*
* Easy part: convert the reload time.
@@ -712,7 +744,7 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp
itp->it_interval = ktime_to_timespec64(timer->it_interval);
if (!expires)
- return;
+ goto out;
/*
* Sample the clock to take the difference with the expiry time.
@@ -732,6 +764,8 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp
itp->it_value.tv_nsec = 1;
itp->it_value.tv_sec = 0;
}
+out:
+ rcu_read_unlock();
}
#define MAX_COLLECTED 20
@@ -952,14 +986,15 @@ static void check_process_timers(struct task_struct *tsk,
static void posix_cpu_timer_rearm(struct k_itimer *timer)
{
clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
- struct cpu_timer *ctmr = &timer->it.cpu;
- struct task_struct *p = ctmr->task;
+ struct task_struct *p;
struct sighand_struct *sighand;
unsigned long flags;
u64 now;
- if (WARN_ON_ONCE(!p))
- return;
+ rcu_read_lock();
+ p = cpu_timer_task_rcu(timer);
+ if (!p)
+ goto out;
/*
* Fetch the current sample and update the timer's expiry time.
@@ -974,13 +1009,15 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer)
/* Protect timer list r/w in arm_timer() */
sighand = lock_task_sighand(p, &flags);
if (unlikely(sighand == NULL))
- return;
+ goto out;
/*
* Now re-arm for the new expiry time.
*/
arm_timer(timer, p);
unlock_task_sighand(p, &flags);
+out:
+ rcu_read_unlock();
}
/**