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From:   Naresh Kamboju <naresh.kamboju@linaro.org>
Date:   Fri, 23 Oct 2020 02:25:19 +0530
Message-ID: <CA+G9fYudry0cXOuSfRTqHKkFKW-sMrA6Z9BdQFmtXsnzqaOgPg@mail.gmail.com>
Subject: Re: mmstress[1309]: segfault at 7f3d71a36ee8 ip 00007f3d77132bdf sp
 00007f3d71a36ee8 error 4 in libc-2.27.so[7f3d77058000+1aa000]
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     open list <linux-kernel@vger.kernel.org>,
        linux-m68k <linux-m68k@lists.linux-m68k.org>,
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        lkft-triage@lists.linaro.org,
        Linux-Next Mailing List <linux-next@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Ingo Molnar <mingo@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        zenglg.jy@cn.fujitsu.com, Stephen Rothwell <sfr@canb.auug.org.au>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Dmitry Vyukov <dvyukov@google.com>
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On Wed, 21 Oct 2020 at 22:52, Naresh Kamboju <naresh.kamboju@linaro.org> wrote:
>
> On Wed, 21 Oct 2020 at 22:35, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > On Wed, Oct 21, 2020 at 9:58 AM Naresh Kamboju
> > <naresh.kamboju@linaro.org> wrote:
> > >
> > > LTP mm mtest05 (mmstress), mtest06_3 and mallocstress01 (mallocstress) tested on
> > > x86 KASAN enabled build. But tests are getting PASS on Non KASAN builds.
> > > This regression started happening from next-20201015 nowards
> >
> > Is it repeatable enough to be bisectable?
>
> Yes. This is easily reproducible.
> I will bisect and report here.

The bad commit points to,

commit d55564cfc222326e944893eff0c4118353e349ec
x86: Make __put_user() generate an out-of-line call

I have reverted this single patch and confirmed the reported
problem is not seen anymore.

- Naresh