Messages in this thread | | | Date | Tue, 10 Sep 2019 15:09:36 +0200 | From | Christian Brauner <> | Subject | Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal |
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On Tue, Sep 10, 2019 at 02:44:41PM +0200, Oleg Nesterov wrote: > On 09/10, Eugene Syromiatnikov wrote: > > > > --- a/kernel/fork.c > > +++ b/kernel/fork.c > > @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > > if (copy_from_user(&args, uargs, size)) > > return -EFAULT; > > > > + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) > > + return -EINVAL; > > Hmm. Unless I am totally confused you found a serious bug... > > Without CLONE_THREAD/CLONE_PARENT copy_process() blindly does > > p->exit_signal = args->exit_signal; > > the valid_signal(sig) check in do_notify_parent() mostly saves us, but we > must not allow child->exit_signal < 0, if nothing else this breaks > thread_group_leader(). > > And afaics this patch doesn't fix this? I think we need the valid_signal() > check...
Thanks for sending this patch so quickly after our conversation yesterday, Eugene! We definitely want valid_signal() to verify the signal is ok.
Eugene, can you please update the patch to use valid signal and keep it as a separate patch from the cleanup and selftest patches?
Christian
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