@@ -118,11 +118,9 @@ struct task_group;
#define task_is_running(task) (READ_ONCE((task)->__state) == TASK_RUNNING)
-#define task_is_traced(task) ((READ_ONCE(task->__state) & __TASK_TRACED) != 0)
-
-#define task_is_stopped(task) ((READ_ONCE(task->__state) & __TASK_STOPPED) != 0)
-
-#define task_is_stopped_or_traced(task) ((READ_ONCE(task->__state) & (__TASK_STOPPED | __TASK_TRACED)) != 0)
+#define task_is_traced(task) ((READ_ONCE(task->jobctl) & JOBCTL_TRACED) != 0)
+#define task_is_stopped(task) ((READ_ONCE(task->jobctl) & JOBCTL_STOPPED) != 0)
+#define task_is_stopped_or_traced(task) ((READ_ONCE(task->jobctl) & (JOBCTL_STOPPED | JOBCTL_TRACED)) != 0)
/*
* Special states are those that do not use the normal wait-loop pattern. See
@@ -22,6 +22,9 @@ struct task_struct;
#define JOBCTL_PTRACE_FROZEN_BIT 24 /* frozen for ptrace */
#define JOBCTL_PTRACE_SIGNR_BIT 25 /* ptrace signal number */
+#define JOBCTL_STOPPED_BIT 26 /* do_signal_stop() */
+#define JOBCTL_TRACED_BIT 27 /* ptrace_stop() */
+
#define JOBCTL_STOP_DEQUEUED (1UL << JOBCTL_STOP_DEQUEUED_BIT)
#define JOBCTL_STOP_PENDING (1UL << JOBCTL_STOP_PENDING_BIT)
#define JOBCTL_STOP_CONSUME (1UL << JOBCTL_STOP_CONSUME_BIT)
@@ -33,6 +36,9 @@ struct task_struct;
#define JOBCTL_PTRACE_FROZEN (1UL << JOBCTL_PTRACE_FROZEN_BIT)
#define JOBCTL_PTRACE_SIGNR (1UL << JOBCTL_PTRACE_SIGNR_BIT)
+#define JOBCTL_STOPPED (1UL << JOBCTL_STOPPED_BIT)
+#define JOBCTL_TRACED (1UL << JOBCTL_TRACED_BIT)
+
#define JOBCTL_TRAP_MASK (JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY)
#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK)
@@ -294,8 +294,10 @@ static inline int kernel_dequeue_signal(void)
static inline void kernel_signal_stop(void)
{
spin_lock_irq(¤t->sighand->siglock);
- if (current->jobctl & JOBCTL_STOP_DEQUEUED)
+ if (current->jobctl & JOBCTL_STOP_DEQUEUED) {
+ current->jobctl |= JOBCTL_STOPPED;
set_special_state(TASK_STOPPED);
+ }
spin_unlock_irq(¤t->sighand->siglock);
schedule();
@@ -439,15 +441,24 @@ static inline void signal_wake_up(struct task_struct *t, bool resume)
{
unsigned int state = 0;
if (resume) {
+ unsigned long jmask = JOBCTL_STOPPED;
state = TASK_WAKEKILL;
- if (!(t->jobctl & JOBCTL_PTRACE_FROZEN))
+ if (!(t->jobctl & JOBCTL_PTRACE_FROZEN)) {
+ jmask |= JOBCTL_TRACED;
state |= __TASK_TRACED;
+ }
+ t->jobctl &= ~jmask;
}
signal_wake_up_state(t, state);
}
static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)
{
- signal_wake_up_state(t, resume ? __TASK_TRACED : 0);
+ unsigned int state = 0;
+ if (resume) {
+ t->jobctl &= ~JOBCTL_TRACED;
+ state = __TASK_TRACED;
+ }
+ signal_wake_up_state(t, state);
}
void task_join_group_stop(struct task_struct *task);
@@ -185,7 +185,12 @@ static bool looks_like_a_spurious_pid(struct task_struct *task)
return true;
}
-/* Ensure that nothing can wake it up, even SIGKILL */
+/*
+ * Ensure that nothing can wake it up, even SIGKILL
+ *
+ * A task is switched to this state while a ptrace operation is in progress;
+ * such that the ptrace operation is uninterruptible.
+ */
static bool ptrace_freeze_traced(struct task_struct *task)
{
bool ret = false;
@@ -216,8 +221,10 @@ static void ptrace_unfreeze_traced(struct task_struct *task)
*/
if (lock_task_sighand(task, &flags)) {
task->jobctl &= ~JOBCTL_PTRACE_FROZEN;
- if (__fatal_signal_pending(task))
+ if (__fatal_signal_pending(task)) {
+ task->jobctl &= ~TASK_TRACED;
wake_up_state(task, __TASK_TRACED);
+ }
unlock_task_sighand(task, &flags);
}
}
@@ -462,8 +469,10 @@ static int ptrace_attach(struct task_struct *task, long request,
* in and out of STOPPED are protected by siglock.
*/
if (task_is_stopped(task) &&
- task_set_jobctl_pending(task, JOBCTL_TRAP_STOP | JOBCTL_TRAPPING))
+ task_set_jobctl_pending(task, JOBCTL_TRAP_STOP | JOBCTL_TRAPPING)) {
+ task->jobctl &= ~JOBCTL_STOPPED;
signal_wake_up_state(task, __TASK_STOPPED);
+ }
spin_unlock(&task->sighand->siglock);
@@ -879,7 +888,7 @@ static int ptrace_resume(struct task_struct *child, long request,
*/
spin_lock_irq(&child->sighand->siglock);
child->exit_code = data;
- child->jobctl |= JOBCTL_PTRACE_SIGNR;
+ child->jobctl = (child->jobctl | JOBCTL_PTRACE_SIGNR) & ~JOBCTL_TRACED;
wake_up_state(child, __TASK_TRACED);
spin_unlock_irq(&child->sighand->siglock);
@@ -762,7 +762,10 @@ static int dequeue_synchronous_signal(kernel_siginfo_t *info)
*/
void signal_wake_up_state(struct task_struct *t, unsigned int state)
{
+ lockdep_assert_held(&t->sighand->siglock);
+
set_tsk_thread_flag(t, TIF_SIGPENDING);
+
/*
* TASK_WAKEKILL also means wake it up in the stopped/traced/killable
* case. We don't check t->state here because there is a race with it
@@ -930,9 +933,10 @@ static bool prepare_signal(int sig, struct task_struct *p, bool force)
for_each_thread(p, t) {
flush_sigqueue_mask(&flush, &t->pending);
task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING);
- if (likely(!(t->ptrace & PT_SEIZED)))
+ if (likely(!(t->ptrace & PT_SEIZED))) {
+ t->jobctl &= ~JOBCTL_STOPPED;
wake_up_state(t, __TASK_STOPPED);
- else
+ } else
ptrace_trap_notify(t);
}
@@ -2208,8 +2212,10 @@ static int ptrace_stop(int exit_code, int why, int clear_code,
spin_lock_irq(¤t->sighand->siglock);
}
- if (!__fatal_signal_pending(current))
+ if (!__fatal_signal_pending(current)) {
set_special_state(TASK_TRACED);
+ current->jobctl |= JOBCTL_TRACED;
+ }
/*
* We're committing to trapping. TRACED should be visible before
@@ -2301,6 +2307,7 @@ static int ptrace_stop(int exit_code, int why, int clear_code,
/* LISTENING can be set only during STOP traps, clear it */
current->jobctl &= ~(JOBCTL_LISTENING | JOBCTL_PTRACE_FROZEN | JOBCTL_PTRACE_SIGNR);
+ WARN_ON_ONCE(current->jobctl & JOBCTL_TRACED);
/*
* Queued signals ignored us while we were stopped for tracing.
@@ -2433,6 +2440,7 @@ static bool do_signal_stop(int signr)
if (task_participate_group_stop(current))
notify = CLD_STOPPED;
+ current->jobctl |= JOBCTL_STOPPED;
set_special_state(TASK_STOPPED);
spin_unlock_irq(¤t->sighand->siglock);
@@ -2454,6 +2462,8 @@ static bool do_signal_stop(int signr)
/* Now we don't run again until woken by SIGCONT or SIGKILL */
cgroup_enter_frozen();
freezable_schedule();
+
+ WARN_ON_ONCE(READ_ONCE(current->jobctl) & JOBCTL_STOPPED);
return true;
} else {
/*
Currently ptrace_stop() / do_signal_stop() rely on the special states TASK_TRACED and TASK_STOPPED resp. to keep unique state. That is, this state exists only in task->__state and nowhere else. There's two spots of bother with this: - PREEMPT_RT has task->saved_state which complicates matters, meaning task_is_{traced,stopped}() needs to check an additional variable. - An alternative freezer implementation that itself relies on a special TASK state would loose TASK_TRACED/TASK_STOPPED and will result in misbehaviour. As such, add additional state to task->jobctl to track this state outside of task->__state. NOTE: this doesn't actually fix anything yet, just adds extra state. --EWB * didn't add a unnecessary newline in signal.h * Update t->jobctl in signal_wake_up and ptrace_signal_wake_up instead of in signal_wake_up_state. This prevents the clearing of TASK_STOPPED and TASK_TRACED from getting lost. * Added warnings if JOBCTL_STOPPED or JOBCTL_TRACED are not cleared Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20220421150654.757693825@infradead.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> --- include/linux/sched.h | 8 +++----- include/linux/sched/jobctl.h | 6 ++++++ include/linux/sched/signal.h | 17 ++++++++++++++--- kernel/ptrace.c | 17 +++++++++++++---- kernel/signal.c | 16 +++++++++++++--- 5 files changed, 49 insertions(+), 15 deletions(-)