linux-kernel - Re: [PATCH] posix-timers: fix stack info leak in timer

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Date:	Mon, 6 Oct 2014 00:28:58 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Mathias Krause <minipli@...glemail.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Brad Spengler <spender@...ecurity.net>,
	PaX Team <pageexec@...email.hu>
Subject: Re: [PATCH] posix-timers: fix stack info leak in timer_create()

On 10/05, Mathias Krause wrote:
>
> On 5 October 2014 23:06, Oleg Nesterov <oleg@...hat.com> wrote:
> > On 10/04, Mathias Krause wrote:
> >>
> >> Cc: <stable@...r.kernel.org>  # v2.6.28+
> >
> > not sure this is -stable material but I won't really argue.
> >
>
> This should fall into the class "security fixes". Info leaks like that
> -- if flagged as such -- got backported regularly in the past. They
> tend to get CVE IDs, even.

And imo, very often we do this for absolutely no reason. Like this fix
tries to do ;) But again, I won't really argue.

> >> --- a/kernel/time/posix-timers.c
> >> +++ b/kernel/time/posix-timers.c
> >> @@ -636,6 +636,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
> >>                       goto out;
> >>               }
> >>       } else {
> >> +             memset(&event.sigev_value, 0, sizeof(event.sigev_value));
> >>               event.sigev_notify = SIGEV_SIGNAL;
> >>               event.sigev_signo = SIGALRM;
> >>               event.sigev_value.sival_int = new_timer->it_id;
> >
> > How about
> >
> >         -       event.sigev_value.sival_int = new_timer->it_id;
> >         +       event.sigev_value = (sigval_t) { .sival_int = new_timer_id };
> >
> > ?
>
> Oh, well. It's a matter of taste, I guess.

Sure.

> It won't fit mine ;) I
> think it makes it slightly less readable.

To me it looks more readable, that is why I suggested this change.
But of course, of course, this is subjective, so I won't insist.

So I think this patch is fine.

Oleg.

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