linux-kernel - Re: [PATCH -next] fork: silence a false postive warning in _

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] [day] [month] [year] [list]

Message-ID: <20200908175808.GX1362448@hirez.programming.kicks-ass.net>
Date:   Tue, 8 Sep 2020 19:58:08 +0200
From:   peterz@...radead.org
To:     Qian Cai <cai@....pw>
Cc:     mark.rutland@....com, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH -next] fork: silence a false postive warning in __mmdrop

On Tue, Sep 08, 2020 at 12:50:44PM -0400, Qian Cai wrote:
> > No, you're talking nonsense. We must not free @mm when
> > 'current->active_mm == mm', never.
> 
> Yes, you are right. It still trigger this below on powerpc with today's
> linux-next by fuzzing for a while (saw a few times on recent linux-next before
> as well but so far mostly reproducible on powerpc here). Any idea?

If you can reliably reproduce this, the next thing is to trace mm_count
and figure out where it goes side-ways. I suppose we're looking for an
'extra' decrement.

Mark tried this for a while but gave up because he couldn't reliably
reproduce.