From dcace06cc29df927a74a6bc0e57b9bef87704377 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 8 Jul 2011 19:13:54 +0200 Subject: [PATCH] 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 Acked-by: Tejun Heo --- include/linux/ptrace.h | 3 +++ kernel/fork.c | 12 ------------ 2 files changed, 3 insertions(+), 12 deletions(-) diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index fd8669fc339f..9b5d2c901d06 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -227,6 +227,9 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace) 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 3c72a5b321a7..4d4117e01504 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -37,7 +37,6 @@ #include #include #include -#include #include #include #include @@ -1521,17 +1520,6 @@ long do_fork(unsigned long clone_flags, 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 -- 2.39.2