From: Oleg Nesterov <oleg@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>,
kernel test robot <xiaolong.ye@intel.com>,
Michal Hocko <mhocko@suse.com>,
LKML <linux-kernel@vger.kernel.org>, LKP <lkp@01.org>
Subject: Re: [lkp-robot] [mm] 1be7107fbe: kernel_BUG_at_mm/mmap.c
Date: Wed, 21 Jun 2017 22:56:17 +0200 [thread overview]
Message-ID: <20170621205617.GA29841@redhat.com> (raw)
In-Reply-To: <CA+55aFyupxx0K6SCi5_vd5nt0FmUYrYGF6yB+k9F+9zbgMwsiQ@mail.gmail.com>
On 06/21, Linus Torvalds wrote:
>
> On Wed, Jun 21, 2017 at 1:27 PM, Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > Now __do_page_fault() tries to expand the stack itself, and this check
> > fails.
>
> But we want that check to trigger and cause the access to fail.
> Accessing the stack below the stack pointer is wrong.
I understand. My point is that this check was invalidated by stack-guard-page
a long ago, and this means that we add the user-visible change now.
> Do you have a pointer to the report for this regression? I must have missed it.
See http://marc.info/?t=149794523000001&r=1&w=2
this thread is a bit confusing, the most relevant emails are
http://marc.info/?l=linux-kernel&m=149806256621440&w=2 (with test case)
http://marc.info/?l=linux-kernel&m=149806452322233&w=2
Actually, I got another (redhat internal) bug report after this discussion,
and at first glance this is the same thing.
Just in case, I agree that mmap(MAP_GROWSDOWN) is mostly useless, perhaps
we do not even care. But still this is regression.
Oleg.
next prev parent reply other threads:[~2017-06-21 20:56 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-21 2:35 [lkp-robot] [mm] 1be7107fbe: kernel_BUG_at_mm/mmap.c kernel test robot
2017-06-21 2:41 ` Hugh Dickins
2017-06-21 18:29 ` Linus Torvalds
2017-06-21 19:33 ` Oleg Nesterov
2017-06-21 19:39 ` Linus Torvalds
2017-06-21 20:27 ` Oleg Nesterov
2017-06-21 20:30 ` Linus Torvalds
2017-06-21 20:56 ` Oleg Nesterov [this message]
2017-06-21 22:19 ` Linus Torvalds
2017-06-22 1:07 ` Hugh Dickins
2017-06-22 10:58 ` Dmitry Safonov
2017-06-22 15:16 ` Oleg Nesterov
2017-06-22 18:04 ` Hugh Dickins
2017-06-22 20:51 ` Oleg Nesterov
2017-06-22 4:23 ` Hugh Dickins
2017-06-21 19:39 ` Hugh Dickins
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