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

From: Ethan Zhao <xerces.zhao@gmail.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Ethan Zhao <haifeng.zhao@intel.com>,
	Bjorn Helgaas <bhelgaas@google.com>, Oliver <oohall@gmail.com>,
	ruscur@russell.cc, Lukas Wunner <lukas@wunner.de>,
	Stuart Hayes <stuart.w.hayes@gmail.com>,
	Alexandru Gagniuc <mr.nuke.me@gmail.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	linux-pci <linux-pci@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"Jia, Pei P" <pei.p.jia@intel.com>
Subject: Re: [PATCH 3/5] PCI/ERR: get device before call device driver to avoid null pointer reference
Date: Tue, 29 Sep 2020 17:38:00 +0800	[thread overview]
Message-ID: <CAKF3qh28CLbt7N2MJ8WE318wYU4kFe+F5Uew3znVJ17yyTR7OA@mail.gmail.com> (raw)
In-Reply-To: <20200929085105.GA3956970@smile.fi.intel.com>

Andy,

On Tue, Sep 29, 2020 at 4:51 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> 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@linux.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.

So git history wouldn't give any of the Oops context, and he/she has
to access LKML,
if offline, then ...lost.

Thanks,
Ethan
>
> --
> With Best Regards,
> Andy Shevchenko
>
>