1 files changed, 10 insertions, 9 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index f6d8b8cb5e34..9439bd3331a6 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -172,6 +172,8 @@ int ptrace_attach(struct task_struct *task)
         audit_ptrace(task);
 
         retval = -EPERM;
+        if (unlikely(task->flags & PF_KTHREAD))
+                goto out;
         if (same_thread_group(task, current))
                 goto out;
 
@@ -182,8 +184,6 @@ int ptrace_attach(struct task_struct *task)
         retval = mutex_lock_interruptible(&task->cred_guard_mutex);
         if (retval  < 0)
                 goto out;
-
-        retval = -EPERM;
 repeat:
         /*
          * Nasty, nasty.
@@ -203,23 +203,24 @@ repeat:
                 goto repeat;
         }
 
-        if (!task->mm)
-                goto bad;
-        /* the same process cannot be attached many times */
-        if (task->ptrace & PT_PTRACED)
-                goto bad;
         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
         if (retval)
                 goto bad;
 
-        /* Go */
+        retval = -EPERM;
+        if (unlikely(task->exit_state))
+                goto bad;
+        if (task->ptrace & PT_PTRACED)
+                goto bad;
+
         task->ptrace |= PT_PTRACED;
         if (capable(CAP_SYS_PTRACE))
                 task->ptrace |= PT_PTRACE_CAP;
 
         __ptrace_link(task, current);
-
         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
+
+        retval = 0;
 bad:
         write_unlock_irqrestore(&tasklist_lock, flags);
         task_unlock(task);