OpenE2K
/
linux
6
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

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>
This commit is contained in:
Oleg Nesterov 2011-07-08 19:13:54 +02:00
parent 6634ae1033
commit dcace06cc2
2 changed files with 3 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/ptrace.h
View File

@ -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);
}
}

12
kernel/fork.c
View File

@ -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>
@ -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