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, 1 insertions, 12 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index eb9934a82fc1..1f2c15297f2d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1514,18 +1514,7 @@ static int wait_task_continued(struct task_struct *p, int noreap,
 
 static inline int my_ptrace_child(struct task_struct *p)
 {
-        if (!(p->ptrace & PT_PTRACED))
-                return 0;
-        if (!(p->ptrace & PT_ATTACHED))
-                return 1;
-        /*
-         * This child was PTRACE_ATTACH'd.  We should be seeing it only if
-         * we are the attacher.  If we are the real parent, this is a race
-         * inside ptrace_attach.  It is waiting for the tasklist_lock,
-         * which we have to switch the parent links, but has already set
-         * the flags in p->ptrace.
-         */
-        return (p->parent != p->real_parent);
+        return p->ptrace & PT_PTRACED;
 }
 
 static long do_wait(pid_t pid, int options, struct siginfo __user *infop,