From: Oleg Nesterov <oleg@redhat.com>

[PATCH] signals: check ->group_stop_count after tracehook_get_signal()

Move the call to do_signal_stop() down, after tracehook call.
This makes ->group_stop_count condition visible to tracers before
do_signal_stop() will participate in this group-stop.

Currently the patch has no effect, tracehook_get_signal() always
returns 0.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Roland McGrath <roland@redhat.com>
---
 include/linux/ptrace.h    |    1 +
 include/linux/sched.h     |    1 +
 include/linux/tracehook.h |   10 +++++-----
 kernel/ptrace.c           |    2 +-
 kernel/signal.c           |    4 ++--
 5 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 4272521..a85fb41 100644  
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -105,6 +105,7 @@ extern int ptrace_traceme(void);
 extern int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len);
 extern int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len);
 extern int ptrace_attach(struct task_struct *tsk);
+extern bool __ptrace_detach(struct task_struct *tracer, struct task_struct *tracee);
 extern int ptrace_detach(struct task_struct *, unsigned int);
 extern void ptrace_disable(struct task_struct *);
 extern int ptrace_check_attach(struct task_struct *task, int kill);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index ce160d6..5e7cc95 100644  
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2030,6 +2030,7 @@ extern int kill_pgrp(struct pid *pid, in
 extern int kill_pid(struct pid *pid, int sig, int priv);
 extern int kill_proc_info(int, struct siginfo *, pid_t);
 extern int do_notify_parent(struct task_struct *, int);
+extern void do_notify_parent_cldstop(struct task_struct *, int);
 extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
 extern void force_sig(int, struct task_struct *);
 extern int send_sig(int, struct task_struct *, int);
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 10db010..c78b2f4 100644  
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -134,7 +134,7 @@ static inline __must_check int tracehook
  */
 static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
 {
-	if (step) {
+	if (step && (task_ptrace(current) & PT_PTRACED)) {
 		siginfo_t info;
 		user_single_step_siginfo(current, regs, &info);
 		force_sig_info(SIGTRAP, &info, current);
@@ -156,7 +156,7 @@ static inline int tracehook_unsafe_exec(
 {
 	int unsafe = 0;
 	int ptrace = task_ptrace(task);
-	if (ptrace & PT_PTRACED) {
+	if (ptrace) {
 		if (ptrace & PT_PTRACE_CAP)
 			unsafe |= LSM_UNSAFE_PTRACE_CAP;
 		else
@@ -178,7 +178,7 @@ static inline int tracehook_unsafe_exec(
  */
 static inline struct task_struct *tracehook_tracer_task(struct task_struct *tsk)
 {
-	if (task_ptrace(tsk) & PT_PTRACED)
+	if (task_ptrace(tsk))
 		return rcu_dereference(tsk->parent);
 	return NULL;
 }
@@ -386,7 +386,7 @@ static inline void tracehook_signal_hand
 					    const struct k_sigaction *ka,
 					    struct pt_regs *regs, int stepping)
 {
-	if (stepping)
+	if (stepping && (task_ptrace(current) & PT_PTRACED))
 		ptrace_notify(SIGTRAP);
 }
 
@@ -492,7 +492,7 @@ static inline int tracehook_get_signal(s
  */
 static inline int tracehook_notify_jctl(int notify, int why)
 {
-	return notify ?: (current->ptrace & PT_PTRACED) ? why : 0;
+	return notify ?: task_ptrace(current) ? why : 0;
 }
 
 /**
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index f34d798..8049cb5 100644  
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -270,7 +270,7 @@ static int ignoring_children(struct sigh
  * reap it now, in that case we must also wake up sub-threads sleeping in
  * do_wait().
  */
-static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
+bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 {
 	__ptrace_unlink(p);
 
diff --git a/kernel/signal.c b/kernel/signal.c
index bded651..6d13d9f 100644  
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1521,7 +1521,7 @@ int do_notify_parent(struct task_struct 
 	return ret;
 }
 
-static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
+void do_notify_parent_cldstop(struct task_struct *tsk, int why)
 {
 	struct siginfo info;
 	unsigned long flags;
@@ -1791,7 +1791,7 @@ static int do_signal_stop(int signr)
 static int ptrace_signal(int signr, siginfo_t *info,
 			 struct pt_regs *regs, void *cookie)
 {
-	if (!task_ptrace(current))
+	if (!(task_ptrace(current) & PT_PTRACED))
 		return signr;
 
 	ptrace_signal_deliver(regs, cookie);