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/tracehook.h b/include/linux/tracehook.h
index ab3ef7aefa95..b48d81969574 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -280,7 +280,7 @@ static inline void tracehook_report_clone(int trace, struct pt_regs *regs,
                                           unsigned long clone_flags,
                                           pid_t pid, struct task_struct *child)
 {
-        if (unlikely(trace)) {
+        if (unlikely(trace) || unlikely(clone_flags & CLONE_PTRACE)) {
                 /*
                  * The child starts up with an immediate SIGSTOP.
                  */