ptrace: mv send-SIGSTOP from do_fork() to ptrace_init_task()
If the new child is traced, do_fork() adds the pending SIGSTOP.
It assumes that either it is traced because of auto-attach or the
tracer attached later, in both cases sigaddset/set_thread_flag is
correct even if SIGSTOP is already pending.
Now that we have PTRACE_SEIZE this is no longer right in the latter
case. If the tracer does PTRACE_SEIZE after copy_process() makes the
child visible the queued SIGSTOP is wrong.
We could check PT_SEIZED bit and change ptrace_attach() to set both
PT_PTRACED and PT_SEIZED bits simultaneously but see the next patch,
we need to know whether this child was auto-attached or not anyway.
So this patch simply moves this code to ptrace_init_task(), this
way we can never race with ptrace_attach().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index fd8669f..9b5d2c9 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -227,6 +227,9 @@
if (unlikely(ptrace) && current->ptrace) {
child->ptrace = current->ptrace;
__ptrace_link(child, current->parent);
+
+ sigaddset(&child->pending.signal, SIGSTOP);
+ set_tsk_thread_flag(child, TIF_SIGPENDING);
}
}
diff --git a/kernel/fork.c b/kernel/fork.c
index 3c72a5b..4d4117e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -37,7 +37,6 @@
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/jiffies.h>
-#include <linux/tracehook.h>
#include <linux/futex.h>
#include <linux/compat.h>
#include <linux/kthread.h>
@@ -1522,17 +1521,6 @@
audit_finish_fork(p);
/*
- * Child is ready but hasn't started running yet. Queue
- * SIGSTOP if it's gonna be ptraced - it doesn't matter who
- * attached/attaching to this task, the pending SIGSTOP is
- * right in any case.
- */
- if (unlikely(p->ptrace)) {
- sigaddset(&p->pending.signal, SIGSTOP);
- set_tsk_thread_flag(p, TIF_SIGPENDING);
- }
-
- /*
* We set PF_STARTING at creation in case tracing wants to
* use this to distinguish a fully live task from one that
* hasn't finished SIGSTOP raising yet. Now we clear it