Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa...

[karo-tx-linux.git] / kernel / ptrace.c

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 227fec36b12a7b2650a77fd58a9cdb5e18c3e8f1..c8e0e050a36afb0ccb875e13d9f2b526b0af4d29 100644 (file)
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -456,8 +456,6 @@ static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 
 static int ptrace_detach(struct task_struct *child, unsigned int data)
 {
-       bool dead = false;
-
        if (!valid_signal(data))
                return -EIO;
 
@@ -467,18 +465,19 @@ static int ptrace_detach(struct task_struct *child, unsigned int data)
 
        write_lock_irq(&tasklist_lock);
        /*
-        * This child can be already killed. Make sure de_thread() or
-        * our sub-thread doing do_wait() didn't do release_task() yet.
+        * We rely on ptrace_freeze_traced(). It can't be killed and
+        * untraced by another thread, it can't be a zombie.
         */
-       if (child->ptrace) {
-               child->exit_code = data;
-               dead = __ptrace_detach(current, child);
-       }
+       WARN_ON(!child->ptrace || child->exit_state);
+       /*
+        * tasklist_lock avoids the race with wait_task_stopped(), see
+        * the comment in ptrace_resume().
+        */
+       child->exit_code = data;
+       __ptrace_detach(current, child);
        write_unlock_irq(&tasklist_lock);
 
        proc_ptrace_connector(child, PTRACE_DETACH);
-       if (unlikely(dead))
-               release_task(child);
 
        return 0;
 }
@@ -697,6 +696,8 @@ static int ptrace_peek_siginfo(struct task_struct *child,
 static int ptrace_resume(struct task_struct *child, long request,
                         unsigned long data)
 {
+       bool need_siglock;
+
        if (!valid_signal(data))
                return -EIO;
 
@@ -724,8 +725,26 @@ static int ptrace_resume(struct task_struct *child, long request,
                user_disable_single_step(child);
        }
 
+       /*
+        * Change ->exit_code and ->state under siglock to avoid the race
+        * with wait_task_stopped() in between; a non-zero ->exit_code will
+        * wrongly look like another report from tracee.
+        *
+        * Note that we need siglock even if ->exit_code == data and/or this
+        * status was not reported yet, the new status must not be cleared by
+        * wait_task_stopped() after resume.
+        *
+        * If data == 0 we do not care if wait_task_stopped() reports the old
+        * status and clears the code too; this can't race with the tracee, it
+        * takes siglock after resume.
+        */
+       need_siglock = data && !thread_group_empty(current);
+       if (need_siglock)
+               spin_lock_irq(&child->sighand->siglock);
        child->exit_code = data;
        wake_up_state(child, __TASK_TRACED);
+       if (need_siglock)
+               spin_unlock_irq(&child->sighand->siglock);
 
        return 0;
 }