tracehook: fix CLONE_PTRACE

In the change in commit 09a05394fe2448a4139b014936330af23fa7ec83, I
overlooked two nits in the logic and this broke using CLONE_PTRACE
when PTRACE_O_TRACE* are not being used.

A parent that is itself traced at all but not using PTRACE_O_TRACE*,
using CLONE_PTRACE would have its new child fail to be traced.

A parent that is not itself traced at all that uses CLONE_PTRACE
(which should be a no-op in this case) would confuse the bookkeeping
and lead to a crash at exit time.

This restores the missing checks and fixes both failure modes.

Reported-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Roland McGrath <roland@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index fd31756e1a00..ea7416c901d1 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -172,7 +172,7 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
         child->ptrace = 0;
         if (unlikely(ptrace)) {
                 child->ptrace = current->ptrace;
-                __ptrace_link(child, current->parent);
+                ptrace_link(child, current->parent);
         }
 }