ptrace: PTRACE_LISTEN forgets to unlock ->siglock

If PTRACE_LISTEN fails after lock_task_sighand() it doesn't drop ->siglock.

Reported-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 9de3ecf..a70d2a5 100644 (file)
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -744,20 +744,17 @@ int ptrace_request(struct task_struct *child, long request,
                        break;
 
                si = child->last_siginfo;
-               if (unlikely(!si || si->si_code >> 8 != PTRACE_EVENT_STOP))
-                       break;
-
-               child->jobctl |= JOBCTL_LISTENING;
-
-               /*
-                * If NOTIFY is set, it means event happened between start
-                * of this trap and now.  Trigger re-trap immediately.
-                */
-               if (child->jobctl & JOBCTL_TRAP_NOTIFY)
-                       signal_wake_up(child, true);
-
+               if (likely(si && (si->si_code >> 8) == PTRACE_EVENT_STOP)) {
+                       child->jobctl |= JOBCTL_LISTENING;
+                       /*
+                        * If NOTIFY is set, it means event happened between
+                        * start of this trap and now.  Trigger re-trap.
+                        */
+                       if (child->jobctl & JOBCTL_TRAP_NOTIFY)
+                               signal_wake_up(child, true);
+                       ret = 0;
+               }
                unlock_task_sighand(child, &flags);
-               ret = 0;
                break;
 
        case PTRACE_DETACH:      /* detach a process that was attached. */