kill PT_ATTACHED

Since the patch

	"Fix ptrace_attach()/ptrace_traceme()/de_thread() race"
	commit f5b40e363ad6041a96e3da32281d8faa191597b9

we set PT_ATTACHED and change child->parent "atomically" wrt task_list lock.

This means we can remove the checks like "PT_ATTACHED && ->parent != ptracer"
which were needed to catch the "ptrace attach is in progress" case.  We can
also remove the flag itself since nobody else uses it.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 4 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 628b03ab88a5..2dc00298e678 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -100,8 +100,7 @@ int ptrace_check_attach(struct task_struct *child, int kill)
          */
         read_lock(&tasklist_lock);
         if ((child->ptrace & PT_PTRACED) && child->parent == current &&
-            (!(child->ptrace & PT_ATTACHED) || child->real_parent != current)
-            && child->signal != NULL) {
+             child->signal != NULL) {
                 ret = 0;
                 spin_lock_irq(&child->sighand->siglock);
                 if (task_is_stopped(child))
@@ -200,8 +199,7 @@ repeat:
                 goto bad;
 
         /* Go */
-        task->ptrace |= PT_PTRACED | ((task->real_parent != current)
-                                      ? PT_ATTACHED : 0);
+        task->ptrace |= PT_PTRACED;
         if (capable(CAP_SYS_PTRACE))
                 task->ptrace |= PT_PTRACE_CAP;