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Message-Id: <20220426225211.308418-9-ebiederm@xmission.com>
Date: Tue, 26 Apr 2022 17:52:11 -0500
From: "Eric W. Biederman" <ebiederm@...ssion.com>
To: linux-kernel@...r.kernel.org
Cc: rjw@...ysocki.net, Oleg Nesterov <oleg@...hat.com>,
mingo@...nel.org, vincent.guittot@...aro.org,
dietmar.eggemann@....com, rostedt@...dmis.org, mgorman@...e.de,
bigeasy@...utronix.de, Will Deacon <will@...nel.org>,
tj@...nel.org, linux-pm@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>,
Richard Weinberger <richard@....at>,
Anton Ivanov <anton.ivanov@...bridgegreys.com>,
Johannes Berg <johannes@...solutions.net>,
linux-um@...ts.infradead.org, Chris Zankel <chris@...kel.net>,
Max Filippov <jcmvbkbc@...il.com>,
inux-xtensa@...ux-xtensa.org, Kees Cook <keescook@...omium.org>,
Jann Horn <jannh@...gle.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 9/9] ptrace: Don't change __state
Stop playing with tsk->__state to remove TASK_WAKEKILL while a ptrace
command is executing.
Instead implement a new jobtl flag JOBCTL_DELAY_WAKEKILL. This new
flag is set in jobctl_freeze_task and cleared when ptrace_stop is
awoken or in jobctl_unfreeze_task (when ptrace_stop remains asleep).
In signal_wake_up_state drop TASK_WAKEKILL from state if TASK_WAKEKILL
is used while JOBCTL_DELAY_WAKEKILL is set. This has the same effect
as changing TASK_TRACED to __TASK_TRACED as all of the wake_ups that
use TASK_KILLABLE go through signal_wake_up except the wake_up in
ptrace_unfreeze_traced.
Previously the __state value of __TASK_TRACED was changed to
TASK_RUNNING when woken up or back to TASK_TRACED when the code was
left in ptrace_stop. Now when woken up ptrace_stop now clears
JOBCTL_DELAY_WAKEKILL and when left sleeping ptrace_unfreezed_traced
clears JOBCTL_DELAY_WAKEKILL.
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
include/linux/sched/jobctl.h | 2 ++
include/linux/sched/signal.h | 3 ++-
kernel/ptrace.c | 11 +++++------
kernel/signal.c | 1 +
4 files changed, 10 insertions(+), 7 deletions(-)
diff --git a/include/linux/sched/jobctl.h b/include/linux/sched/jobctl.h
index fa067de9f1a9..4e154ad8205f 100644
--- a/include/linux/sched/jobctl.h
+++ b/include/linux/sched/jobctl.h
@@ -19,6 +19,7 @@ struct task_struct;
#define JOBCTL_TRAPPING_BIT 21 /* switching to TRACED */
#define JOBCTL_LISTENING_BIT 22 /* ptracer is listening for events */
#define JOBCTL_TRAP_FREEZE_BIT 23 /* trap for cgroup freezer */
+#define JOBCTL_DELAY_WAKEKILL_BIT 24 /* delay killable wakeups */
#define JOBCTL_STOP_DEQUEUED (1UL << JOBCTL_STOP_DEQUEUED_BIT)
#define JOBCTL_STOP_PENDING (1UL << JOBCTL_STOP_PENDING_BIT)
@@ -28,6 +29,7 @@ struct task_struct;
#define JOBCTL_TRAPPING (1UL << JOBCTL_TRAPPING_BIT)
#define JOBCTL_LISTENING (1UL << JOBCTL_LISTENING_BIT)
#define JOBCTL_TRAP_FREEZE (1UL << JOBCTL_TRAP_FREEZE_BIT)
+#define JOBCTL_DELAY_WAKEKILL (1UL << JOBCTL_DELAY_WAKEKILL_BIT)
#define JOBCTL_TRAP_MASK (JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY)
#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK)
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 3c8b34876744..1947c85aa9d9 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -437,7 +437,8 @@ extern void signal_wake_up_state(struct task_struct *t, unsigned int state);
static inline void signal_wake_up(struct task_struct *t, bool resume)
{
- signal_wake_up_state(t, resume ? TASK_WAKEKILL : 0);
+ bool wakekill = resume && !(t->jobctl & JOBCTL_DELAY_WAKEKILL);
+ signal_wake_up_state(t, wakekill ? TASK_WAKEKILL : 0);
}
static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)
{
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 842511ee9a9f..0bea74539320 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -194,7 +194,7 @@ static bool ptrace_freeze_traced(struct task_struct *task)
if (task_is_traced(task) && !looks_like_a_spurious_pid(task) &&
!__fatal_signal_pending(task)) {
- WRITE_ONCE(task->__state, __TASK_TRACED);
+ task->jobctl |= JOBCTL_DELAY_WAKEKILL;
ret = true;
}
@@ -203,7 +203,7 @@ static bool ptrace_freeze_traced(struct task_struct *task)
static void ptrace_unfreeze_traced(struct task_struct *task)
{
- if (READ_ONCE(task->__state) != __TASK_TRACED)
+ if (!(READ_ONCE(task->jobctl) & JOBCTL_DELAY_WAKEKILL))
return;
WARN_ON(!task->ptrace || task->parent != current);
@@ -213,11 +213,10 @@ static void ptrace_unfreeze_traced(struct task_struct *task)
* Recheck state under the lock to close this race.
*/
spin_lock_irq(&task->sighand->siglock);
- if (READ_ONCE(task->__state) == __TASK_TRACED) {
+ if (task->jobctl & JOBCTL_DELAY_WAKEKILL) {
+ task->jobctl &= ~JOBCTL_DELAY_WAKEKILL;
if (__fatal_signal_pending(task))
wake_up_state(task, __TASK_TRACED);
- else
- WRITE_ONCE(task->__state, TASK_TRACED);
}
spin_unlock_irq(&task->sighand->siglock);
}
@@ -253,7 +252,7 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state)
*/
if (lock_task_sighand(child, &flags)) {
if (child->ptrace && child->parent == current) {
- WARN_ON(READ_ONCE(child->__state) == __TASK_TRACED);
+ WARN_ON(child->jobctl & JOBCTL_DELAY_WAKEKILL);
/*
* child->sighand can't be NULL, release_task()
* does ptrace_unlink() before __exit_signal().
diff --git a/kernel/signal.c b/kernel/signal.c
index 584d67deb3cb..2b332f89cbad 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2307,6 +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;
+ current->jobctl &= ~JOBCTL_DELAY_WAKEKILL;
/*
* Queued signals ignored us while we were stopped for tracing.
--
2.35.3
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