linux-kernel - Re: kernel BUG at mm/highmem.c:417! invalid opcode: 0000 EIP: zero_user

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Date:   Wed, 25 Nov 2020 16:16:47 +0530
From:   Naresh Kamboju <naresh.kamboju@...aro.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        open list <linux-kernel@...r.kernel.org>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, lkft-triage@...ts.linaro.org,
        LTP List <ltp@...ts.linux.it>,
        Andrew Morton <akpm@...ux-foundation.org>,
        torvalds@...uxfoundation.org, Yang Shi <shy828301@...il.com>,
        Jan Kara <jack@...e.cz>, Michal Hocko <mhocko@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mel Gorman <mgorman@...e.de>, Song Liu <songliubraving@...com>,
        Zi Yan <ziy@...dia.com>, vtolkm@...glemail.com,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: kernel BUG at mm/highmem.c:417! invalid opcode: 0000 EIP: zero_user_segments

On Wed, 25 Nov 2020 at 06:16, Matthew Wilcox <willy@...radead.org> wrote:
>
> On Tue, Nov 24, 2020 at 06:16:28PM +0100, Sebastian Andrzej Siewior wrote:
> > On 2020-11-24 18:52:44 [+0530], Naresh Kamboju wrote:
> > > While running LTP test case access01 the following kernel BUG
> > > noticed on linux next 20201124 tag kernel on i386.
> > >
> > > git short log:
> > > ----------------
> > > git log --oneline next-20201120..next-20201124 -- mm/highmem.c
> > > d9927d46febf Merge branch 'akpm-current/current'
> > > 72d22a0d0e86 mm: support THPs in zero_user_segments
> > > 2a656cad337e mm/highmem: Take kmap_high_get() properly into account
> > >
> > > Please find these easy steps to reproduce the kernel build and boot.
> >
> > This BUG_ON() is in zero_user_segments() which ash been added in commit
> >    72d22a0d0e86 mm: support THPs in zero_user_segments
> >
> > > [   50.852189] kernel BUG at mm/highmem.c:417!
> >
> > I managed to capture one invocation with:
> > zero_user_segments(0xd4367a90,
> >                  0x1000, 0x1000,
> >                  0x0, 0x50)
> > page_compound() -> 1
> > page_size() -> 4096
>
> Thanks for debugging this!  I didn't realise start1 was allowed to be
> less than start2.  Try this ... (systemd is sabotaging my efforts to
> test an i386 kernel)

This patch tested on i386, x86_64 and arm and the reported problem got fixed.
Tested-by: Naresh Kamboju <naresh.kamboju@...aro.org>

- Naresh