Re: [PATCH] exec: Limit arg stack to at most _STK_LIM / 4 * 3

From: Linus Torvalds <torvalds@linux-foundation.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Kees Cook <keescook@chromium.org>,
	Andy Lutomirski <luto@kernel.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Ben Hutchings <ben@decadent.org.uk>,
	Hugh Dickins <hughd@google.com>, Oleg Nesterov <oleg@redhat.com>,
	"Jason A. Donenfeld" <Jason@zx2c4.com>,
	Rik van Riel <riel@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] exec: Limit arg stack to at most _STK_LIM / 4 * 3
Date: Mon, 10 Jul 2017 11:24:55 -0700	[thread overview]
Message-ID: <CA+55aFyVQ_cfmHbXKA2DhdmKDu9dg=OFerCXW=D5KqF4W=8sjw@mail.gmail.com> (raw)
In-Reply-To: <20170710155943.GA7071@dhcp22.suse.cz>

On Mon, Jul 10, 2017 at 8:59 AM, Michal Hocko <mhocko@kernel.org> wrote:
>
> We will always need some gap inforcement.

Considering the Java issue, that's rather questionable.

We really can't be breaking libreoffice. That's like a big classic
no-no - it affects normal users that simply cannot be expected to work
around it. For them, it's a "my office application no longer works"
situation, and they just think the system is flaky.

Now, somebody who explicitly raised the stack limit past 24MB and gets
bit because he also tries to use more than 6M of arguments - that's
actually a different issue. Let's see if anybody ever even complains,
and then we might make it a "only for suid binaries" thing.

But honestly, a security limit that isn't tested in normal working is
not a security limit at all, it's just theory and likely bullshit. So
I'd much rather *not* make it suid-specific if at all possible. That
way it has some chance in hell of actually getting tested.

                    Linus