linux-kernel - RE: PCI: Race condition in pci_create_sysfs_dev

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Date:   Thu, 18 Nov 2021 03:42:26 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Krzysztof Wilczyński <kw@...ux.com>,
        Dexuan-Linux Cui <dexuan.linux@...il.com>
CC:     Pali Rohár <pali@...nel.org>,
        Koen Vandeputte <koen.vandeputte@...ymesh.com>,
        Petr Štetiar <ynezz@...e.cz>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>, Yinghai Lu <yinghai@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: RE: PCI: Race condition in pci_create_sysfs_dev_files

> From: Krzysztof Wilczyński <kw@...ux.com>
> Sent: Wednesday, November 17, 2021 7:10 PM
> [...]
> > I think we're seeing the same issue with a Linux VM on Hyper-V.
> 
> Are you still seeing this issue happen?  If so, does it happen often?

This doesn't happen often. It's found by our test team.

> We haven't had a report from a system that runs as a hypervisor guest
> before.  I also assume this is x86 or x86_64 platform, correct?

Yes, x86_64.
 
> > Here the kernel is ...
> >
> This is quite an old kernel, however the 5.4 is a long-term kernel, and
> therefore we need to make sure that it would also work properly.
> 
> >
> '/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBUS:01/475
> 05500-0003-0000-3130-444531334632/pci0003:00/0003:00:00.0/config'
> 
> Following the commit e1d3f3268b0e ("PCI/sysfs: Convert "config" to static
> attribute"), the issue particularly with the "config" attribute should be
> resolved, thus more modern kernel versions are no long suffer from the race
> condition related to this specific and some other problematic attributes.

Thanks for sharing the commit info! It's great to know this has been fixed
in the mainlinekernel.

> We quite likely have to back-port these changes to a number of older
> long-term kernels.  I am going to look into it.

Sounds good! Thank you, Krzysztof!

> Hopefully, once the patches land in upstream long-term kernels, then
> distributions would be able to cherry-pick them and apply to their kernels
> releases.
> 
> 	Krzysztof

Yes, this should work.

Thanks,
-- Dexuan