1 files changed, 78 insertions, 22 deletions

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 9b12d65186f..c2390f41307 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -17,6 +17,7 @@
 #include <linux/slab.h>
 #include <linux/freezer.h>
 #include <linux/ptrace.h>
+#include <linux/uaccess.h>
 #include <trace/events/sched.h>
 
 static DEFINE_SPINLOCK(kthread_create_lock);
@@ -32,7 +33,7 @@ struct kthread_create_info
 
 	/* Result passed back to kthread_create() from kthreadd. */
 	struct task_struct *result;
-	struct completion done;
+	struct completion *done;
 
 	struct list_head list;
 };
@@ -135,6 +136,24 @@ void *kthread_data(struct task_struct *task)
 	return to_kthread(task)->data;
 }
 
+/**
+ * probe_kthread_data - speculative version of kthread_data()
+ * @task: possible kthread task in question
+ *
+ * @task could be a kthread task.  Return the data value specified when it
+ * was created if accessible.  If @task isn't a kthread task or its data is
+ * inaccessible for any reason, %NULL is returned.  This function requires
+ * that @task itself is safe to dereference.
+ */
+void *probe_kthread_data(struct task_struct *task)
+{
+	struct kthread *kthread = to_kthread(task);
+	void *data = NULL;
+
+	probe_kernel_read(&data, &kthread->data, sizeof(data));
+	return data;
+}
+
 static void __kthread_parkme(struct kthread *self)
 {
 	__set_current_state(TASK_PARKED);
@@ -159,6 +178,7 @@ static int kthread(void *_create)
 	struct kthread_create_info *create = _create;
 	int (*threadfn)(void *data) = create->threadfn;
 	void *data = create->data;
+	struct completion *done;
 	struct kthread self;
 	int ret;
 
@@ -168,10 +188,16 @@ static int kthread(void *_create)
 	init_completion(&self.parked);
 	current->vfork_done = &self.exited;
 
+	/* If user was SIGKILLed, I release the structure. */
+	done = xchg(&create->done, NULL);
+	if (!done) {
+		kfree(create);
+		do_exit(-EINTR);
+	}
 	/* OK, tell user we're spawned, wait for stop or wakeup */
 	__set_current_state(TASK_UNINTERRUPTIBLE);
 	create->result = current;
-	complete(&create->done);
+	complete(done);
 	schedule();
 
 	ret = -EINTR;
@@ -191,7 +217,7 @@ int tsk_fork_get_node(struct task_struct *tsk)
 	if (tsk == kthreadd_task)
 		return tsk->pref_node_fork;
 #endif
-	return numa_node_id();
+	return NUMA_NO_NODE;
 }
 
 static void create_kthread(struct kthread_create_info *create)
@@ -204,8 +230,15 @@ static void create_kthread(struct kthread_create_info *create)
 	/* We want our own signal handler (we take no signals by default). */
 	pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
 	if (pid < 0) {
+		/* If user was SIGKILLed, I release the structure. */
+		struct completion *done = xchg(&create->done, NULL);
+
+		if (!done) {
+			kfree(create);
+			return;
+		}
 		create->result = ERR_PTR(pid);
-		complete(&create->done);
+		complete(done);
 	}
 }
 
@@ -229,43 +262,66 @@ static void create_kthread(struct kthread_create_info *create)
  * kthread_stop() has been called).  The return value should be zero
  * or a negative error number; it will be passed to kthread_stop().
  *
- * Returns a task_struct or ERR_PTR(-ENOMEM).
+ * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
  */
 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
 					   void *data, int node,
 					   const char namefmt[],
 					   ...)
 {
-	struct kthread_create_info create;
-
-	create.threadfn = threadfn;
-	create.data = data;
-	create.node = node;
-	init_completion(&create.done);
+	DECLARE_COMPLETION_ONSTACK(done);
+	struct task_struct *task;
+	struct kthread_create_info *create = kmalloc(sizeof(*create),
+						     GFP_KERNEL);
+
+	if (!create)
+		return ERR_PTR(-ENOMEM);
+	create->threadfn = threadfn;
+	create->data = data;
+	create->node = node;
+	create->done = &done;
 
 	spin_lock(&kthread_create_lock);
-	list_add_tail(&create.list, &kthread_create_list);
+	list_add_tail(&create->list, &kthread_create_list);
 	spin_unlock(&kthread_create_lock);
 
 	wake_up_process(kthreadd_task);
-	wait_for_completion(&create.done);
-
-	if (!IS_ERR(create.result)) {
+	/*
+	 * Wait for completion in killable state, for I might be chosen by
+	 * the OOM killer while kthreadd is trying to allocate memory for
+	 * new kernel thread.
+	 */
+	if (unlikely(wait_for_completion_killable(&done))) {
+		/*
+		 * If I was SIGKILLed before kthreadd (or new kernel thread)
+		 * calls complete(), leave the cleanup of this structure to
+		 * that thread.
+		 */
+		if (xchg(&create->done, NULL))
+			return ERR_PTR(-EINTR);
+		/*
+		 * kthreadd (or new kernel thread) will call complete()
+		 * shortly.
+		 */
+		wait_for_completion(&done);
+	}
+	task = create->result;
+	if (!IS_ERR(task)) {
 		static const struct sched_param param = { .sched_priority = 0 };
 		va_list args;
 
 		va_start(args, namefmt);
-		vsnprintf(create.result->comm, sizeof(create.result->comm),
-			  namefmt, args);
+		vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
 		va_end(args);
 		/*
 		 * root may have changed our (kthreadd's) priority or CPU mask.
 		 * The kernel thread should not inherit these properties.
 		 */
-		sched_setscheduler_nocheck(create.result, SCHED_NORMAL, &param);
-		set_cpus_allowed_ptr(create.result, cpu_all_mask);
+		sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
+		set_cpus_allowed_ptr(task, cpu_all_mask);
 	}
-	return create.result;
+	kfree(create);
+	return task;
 }
 EXPORT_SYMBOL(kthread_create_on_node);
 
@@ -278,7 +334,7 @@ static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
 	}
 	/* It's safe because the task is inactive. */
 	do_set_cpus_allowed(p, cpumask_of(cpu));
-	p->flags |= PF_THREAD_BOUND;
+	p->flags |= PF_NO_SETAFFINITY;
 }
 
 /**
@@ -313,7 +369,7 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
 {
 	struct task_struct *p;
 
-	p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
+	p = kthread_create_on_node(threadfn, data, cpu_to_mem(cpu), namefmt,
 				   cpu);
 	if (IS_ERR(p))
 		return p;