1 files changed, 54 insertions, 10 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 62f7c2774b16..6cbeaae4406d 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -122,6 +122,40 @@ void __ptrace_unlink(struct task_struct *child)
         spin_unlock(&child->sighand->siglock);
 }
 
+/* Ensure that nothing can wake it up, even SIGKILL */
+static bool ptrace_freeze_traced(struct task_struct *task)
+{
+        bool ret = false;
+
+        /* Lockless, nobody but us can set this flag */
+        if (task->jobctl & JOBCTL_LISTENING)
+                return ret;
+
+        spin_lock_irq(&task->sighand->siglock);
+        if (task_is_traced(task) && !__fatal_signal_pending(task)) {
+                task->state = __TASK_TRACED;
+                ret = true;
+        }
+        spin_unlock_irq(&task->sighand->siglock);
+
+        return ret;
+}
+
+static void ptrace_unfreeze_traced(struct task_struct *task)
+{
+        if (task->state != __TASK_TRACED)
+                return;
+
+        WARN_ON(!task->ptrace || task->parent != current);
+
+        spin_lock_irq(&task->sighand->siglock);
+        if (__fatal_signal_pending(task))
+                wake_up_state(task, __TASK_TRACED);
+        else
+                task->state = TASK_TRACED;
+        spin_unlock_irq(&task->sighand->siglock);
+}
+
 /**
  * ptrace_check_attach - check whether ptracee is ready for ptrace operation
  * @child: ptracee to check for
@@ -151,24 +185,29 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state)
          * be changed by us so it's not changing right after this.
          */
         read_lock(&tasklist_lock);
-        if ((child->ptrace & PT_PTRACED) && child->parent == current) {
+        if (child->ptrace && child->parent == current) {
+                WARN_ON(child->state == __TASK_TRACED);
                 /*
                  * child->sighand can't be NULL, release_task()
                  * does ptrace_unlink() before __exit_signal().
                  */
-                spin_lock_irq(&child->sighand->siglock);
-                WARN_ON_ONCE(task_is_stopped(child));
-                if (ignore_state || (task_is_traced(child) &&
-                                     !(child->jobctl & JOBCTL_LISTENING)))
+                if (ignore_state || ptrace_freeze_traced(child))
                         ret = 0;
-                spin_unlock_irq(&child->sighand->siglock);
         }
         read_unlock(&tasklist_lock);
 
-        if (!ret && !ignore_state)
-                ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;
+        if (!ret && !ignore_state) {
+                if (!wait_task_inactive(child, __TASK_TRACED)) {
+                        /*
+                         * This can only happen if may_ptrace_stop() fails and
+                         * ptrace_stop() changes ->state back to TASK_RUNNING,
+                         * so we should not worry about leaking __TASK_TRACED.
+                         */
+                        WARN_ON(child->state == __TASK_TRACED);
+                        ret = -ESRCH;
+                }
+        }
 
-        /* All systems go.. */
         return ret;
 }
 
@@ -900,6 +939,8 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,
                 goto out_put_task_struct;
 
         ret = arch_ptrace(child, request, addr, data);
+        if (ret || request != PTRACE_DETACH)
+                ptrace_unfreeze_traced(child);
 
  out_put_task_struct:
         put_task_struct(child);
@@ -1039,8 +1080,11 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 
         ret = ptrace_check_attach(child, request == PTRACE_KILL ||
                                   request == PTRACE_INTERRUPT);
-        if (!ret)
+        if (!ret) {
                 ret = compat_arch_ptrace(child, request, addr, data);
+                if (ret || request != PTRACE_DETACH)
+                        ptrace_unfreeze_traced(child);
+        }
 
  out_put_task_struct:
         put_task_struct(child);