linux-kernel - Re: [PATCH] signal: Make the si_code check in rt

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Date:	Mon, 12 Oct 2015 17:37:09 +0100
From:	"Amanieu d'Antras" <amanieu@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH] signal: Make the si_code check in rt_[tg]sigqueueinfo stricter

On Mon, Oct 12, 2015 at 4:54 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> Yes, copy_siginfo_to_user() does __put_user((short)from->si_code).
> But SI_FROMUSER/SI_FROMKERNEL are internal kernel checks, we mostly
> use them in copy_siginfo_to_user().
>
> And note that if ->si_code < 0 we simply do __copy_to_user(), so
> userspace can't see something which looks like "from kernel", in
> this case we do not truncate ->si_code.

Ah my bad, I seem to have missed that case. So copy_siginfo_to_user
seems to be safe, but it is still an issue for copy_siginfo_to_user32
which doesn't have this check.

Maybe this should be fixed in the compat code instead?
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