Re: [small patch] ia64 find thread for user rbs address

["Zhang, Yanmin" <yanmin_zhang@linux.intel.com>]

On Thu, 2006-11-16 at 17:42, bibo,mao wrote:
> Tony,
> please discard this patch. It can not fix completely. If ptrace
> caller wants to access vforked child process's user rbs, there
> will be problem.
The patch is correct.

If ptracer wants to access vforked child process's user rbs,
find_thread_for_addr's first parameter, child, will points to
the vforked task_struct instead of vforker's.

> 
> thanks
> bibo,mao
> 
> bibo,mao wrote:
> > hi,
> >   I encountered one problem when running ptrace test case, the
> > situation is this: traced process's syscall parameter needs to
> > be accessed, but for sys_clone system call with clone_flag
> > (CLONE_VFORK | CLONE_VM | SIGCHLD) parameter. this syscall's
> > parameter accessing result is wrong.
> >   The reason is that with clone_flag(CLONE_VFORK | CLONE_VM | SIGCHLD),
> > cloned thread's mm point is the same, but tgid is different.
> > without this patch find_thread_for_addr will return cloned thread,
> > but not the thread which call sys_clone syscall.
> > 
> > thanks
> > bibo,mao
> > 
> > --- 2.6.19-rc5.org/arch/ia64/kernel/ptrace.c    2006-11-16 16:23:31.000000000 +0800
> > +++ 2.6.19-rc5/arch/ia64/kernel/ptrace.c        2006-11-16 16:25:07.000000000 +0800
> > @@ -607,7 +607,7 @@ find_thread_for_addr (struct task_struct
> >          */
> >         list_for_each_safe(this, next, &current->children) {
> >                 p = list_entry(this, struct task_struct, sibling);
> > -               if (p->mm != mm)
> > +               if (p->tgid != child->tgid)
> >                         continue;
> >                 if (thread_matches(p, addr)) {
> >                         child = p;
> > -