diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2011-07-08 19:13:54 +0200 |
|---|---|---|
| committer | Oleg Nesterov <oleg@redhat.com> | 2011-07-17 20:23:51 +0200 |
| commit | dcace06cc29df927a74a6bc0e57b9bef87704377 (patch) | |
| tree | 9a04518032869b1ed79933026379ea0d7081e43a | |
| parent | 6634ae1033ceaeca5877dd75723210f8c2648c17 (diff) | |
| download | lwn-dcace06cc29df927a74a6bc0e57b9bef87704377.tar.gz lwn-dcace06cc29df927a74a6bc0e57b9bef87704377.zip | |
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>
| -rw-r--r-- | include/linux/ptrace.h | 3 | ||||
| -rw-r--r-- | 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 <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 @@ 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 * hasn't finished SIGSTOP raising yet. Now we clear it |