linux-kernel - Re: WARNING: at mm/mremap.c:211 move_page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=whmbpZN6-Q=8cDM42UmHmqzgNDucLLP4BvR1jQ73+KSgw@mail.gmail.com>
Date:   Sun, 12 Jul 2020 20:51:26 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        linux- stable <stable@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...nel.org>,
        lkft-triage@...ts.linaro.org, Chris Down <chris@...isdown.name>,
        Michel Lespinasse <walken@...gle.com>,
        Fan Yang <Fan_Yang@...u.edu.cn>,
        Brian Geffon <bgeffon@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>, pugaowei@...il.com,
        Jerome Glisse <jglisse@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Hugh Dickins <hughd@...gle.com>,
        Al Viro <viro@...iv.linux.org.uk>, Tejun Heo <tj@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: WARNING: at mm/mremap.c:211 move_page_tables in i386

On Sun, Jul 12, 2020 at 7:53 PM Joel Fernandes <joel@...lfernandes.org> wrote:
>
> > But I do feel like you figured out why the bug happened, now we're
> > just discussing whether the patch is the right thing to do.
>
> Yes.
>
> > Maybe saying "doing the pmd copies for the initial stack isn't
> > important, so let's just note this as a special case and get rid of
> > the WARN_ON()" might be an alternative solution.
>
> Personally, I feel it is better to keep the warning just so in the future we
> can detect any bugs.

I don't disagree, the warning didn't happen to find a bug now, but it
did fine a case we might be able to do better.

So now that I feel we understand the issue, and it's not a horrible
problem, just a (very hard to trigger) warning, I don't think there's
any huge hurry.

I think think I will - for now - change the WARN_ON() to
WARN_ON_ONCE() (so that it doesn't floow the logs if somebody triggers
this odd special case  this malisiously), and add a note about how
this happens to the code for posterito.

And if/when you figure out a better way to fix it, we can update the note.

Ok?

             Linus