On Mon, Apr 22, 2013 at 05:07:10PM +0200, Oleg Nesterov wrote:
> On 04/22, Oleg Nesterov wrote:
> >
> > On 04/22, Andrey Vagin wrote:
> > >
> > > + case PTRACE_SETSIGMASK:
> > > + {
> > > + sigset_t new_set;
> > > +
> > > + if (addr != sizeof(sigset_t)) {
> > > + ret = -EINVAL;
> > > + break;
> > > + }
> > > +
> > > + if (copy_from_user(&new_set, datavp, sizeof(sigset_t))) {
> > > + ret = -EFAULT;
> > > + break;
> > > + }
> > > +
> > > + sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
> > > +
> > > + spin_lock_irq(&child->sighand->siglock);
> > > + __set_task_blocked(child, &new_set);
> > > + spin_unlock_irq(&child->sighand->siglock);
> >
> > No, please don't...
> >
> > set_current_blocked/__set_task_blocked assume that tsk == current.
> > If nothing else, note recalc_sigpending() in __set_task_blocked().
Thank you for the comment. It's my mistake.
> >
> > I don't understand "This method is not suitable for stopped tasks"
For example, a stopped process has a pending signal and this signal is
not blocked. crtools should dump its state, so that the process remains
in a stopped state with the same pending signal.
For dumping state crtools inject a parasite code with help POKE_DATA,
sets %rip on this code (PTRACE_SETREGS) and resumes the task
(PTRACE_CONT).
If signals are not blocked, the kernel starts to handle the signal after
resuming a process. It's out of our plan.
https://lkml.org/lkml/2011/7/20/138 - an example of code for injecting a
parasite code.
I hope the problem is become more clear.
> > from the changelog, but if you really need PTRACE_SETSIGMASK just
> > change ->blocked under siglock and do recalc_sigpending_tsk(child).
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> actually this is not necessary, the tracee will do recalc_sigpending()
> after resume. But perhaps a comment make sense.
__set_task_blocked executes retarget_shared_pending. I think it must be
called here too or am I wrong?
>
> Oleg.
>
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