linux-kernel - Re: [PATCH 3/5] PCI/ERR: get device before call device driver to avoid null pointer reference

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Message-ID: <20200929085105.GA3956970@smile.fi.intel.com>
Date:   Tue, 29 Sep 2020 11:51:05 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Ethan Zhao <xerces.zhao@...il.com>
Cc:     Ethan Zhao <haifeng.zhao@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, Oliver <oohall@...il.com>,
        ruscur@...sell.cc, Lukas Wunner <lukas@...ner.de>,
        Stuart Hayes <stuart.w.hayes@...il.com>,
        Alexandru Gagniuc <mr.nuke.me@...il.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Jia, Pei P" <pei.p.jia@...el.com>
Subject: Re: [PATCH 3/5] PCI/ERR: get device before call device driver to
 avoid null pointer reference

On Tue, Sep 29, 2020 at 10:35:14AM +0800, Ethan Zhao wrote:
> Preferred style, there will be cleared comment in v6.

Avoid top postings.

> On Sat, Sep 26, 2020 at 12:42 AM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> >
> > On Thu, Sep 24, 2020 at 10:34:21PM -0400, Ethan Zhao wrote:
> > > During DPC error injection test we found there is race condition between
> > > pciehp and DPC driver, null pointer reference caused panic as following
> >
> > null -> NULL
> >
> > >
> > >  # setpci -s 64:02.0 0x196.w=000a
> > >   // 64:02.0 is rootport has DPC capability
> > >  # setpci -s 65:00.0 0x04.w=0544
> > >   // 65:00.0 is NVMe SSD populated in above port
> > >  # mount /dev/nvme0n1p1 nvme
> > >
> > >  (tested on stable 5.8 & ICX platform)
> > >
> > >  Buffer I/O error on dev nvme0n1p1, logical block 468843328,
> > >  async page read
> > >  BUG: kernel NULL pointer dereference, address: 0000000000000050
> > >  #PF: supervisor read access in kernel mode
> > >  #PF: error_code(0x0000) - not-present page
> >
> > Same comment about Oops.

In another thread it was a good advice to move the full Oops (if you think it's
very useful to have) after the cutter '---' line, so it will be in email
archives but Git history.

-- 
With Best Regards,
Andy Shevchenko