linux-kernel - Re: [PATCH] PCI/MSI: fix page fault when msi_populate

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Date:   Tue, 12 Oct 2021 15:39:45 +1300
From:   Barry Song <21cnbao@...il.com>
To:     "wanghai (M)" <wanghai38@...wei.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pci@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI/MSI: fix page fault when msi_populate_sysfs() failed

On Tue, Oct 12, 2021 at 3:25 PM wanghai (M) <wanghai38@...wei.com> wrote:
>
>
> 在 2021/10/12 10:09, Bjorn Helgaas 写道:
> > On Tue, Oct 12, 2021 at 09:59:40AM +0800, wanghai (M) wrote:
> >> 在 2021/10/12 1:11, Bjorn Helgaas 写道:
> >>> For v2, please note "git log --oneline drivers/pci/msi.c" and make
> >>> your patch follow the style, including capitalization.
> >>>
> >>> On Mon, Oct 11, 2021 at 05:15:28PM +0800, wanghai (M) wrote:
> >>>> 在 2021/10/11 16:52, Barry Song 写道:
> >>>>> On Mon, Oct 11, 2021 at 9:24 PM Wang Hai <wanghai38@...wei.com> wrote:
> >>>>>> I got a page fault report when doing fault injection test:
> >>> When you send v2, can you include information about how you injected
> >>> the fault?  If it's easy, others can reproduce the failure that way.
> >> Sorry, the reproduction needs to be based on the fault injection framework
> >> provided by Hulk Robot. I don't know how the framework is implemented.
> >>
> >> The way to reproduce this is to do a fault injection to make
> >> 'msi_attrs = kcalloc() in msi_populate_sysfs()' fail when insmod
> >> 9pnet_virtio.ko.
> >>
> >> I sent v2 yesterday, can you help review it?
> >> https://lore.kernel.org/linux-pci/20211011130837.766323-1-wanghai38@huawei.com/
> >>>>>> BUG: unable to handle page fault for address: fffffffffffffff4
> >>>>>> ...
> >>>>>> RIP: 0010:sysfs_remove_groups+0x25/0x60
> >>>>>> ...
> >>>>>> Call Trace:
> >>>>>>     msi_destroy_sysfs+0x30/0xa0
> >>>>>>     free_msi_irqs+0x11d/0x1b0
> >>>>>>     __pci_enable_msix_range+0x67f/0x760
> >>>>>>     pci_alloc_irq_vectors_affinity+0xe7/0x170
> >>>>>>     vp_find_vqs_msix+0x129/0x560
> >>>>>>     vp_find_vqs+0x52/0x230
> >>>>>>     vp_modern_find_vqs+0x47/0xb0
> >>>>>>     p9_virtio_probe+0xa1/0x460 [9pnet_virtio]
> >>>>>>     virtio_dev_probe+0x1ed/0x2e0
> >>>>>>     really_probe+0x1c7/0x400
> >>>>>>     __driver_probe_device+0xa4/0x120
> >>>>>>     driver_probe_device+0x32/0xe0
> >>>>>>     __driver_attach+0xbf/0x130
> >>>>>>     bus_for_each_dev+0xbb/0x110
> >>>>>>     driver_attach+0x27/0x30
> >>>>>>     bus_add_driver+0x1d9/0x270
> >>>>>>     driver_register+0xa9/0x180
> >>>>>>     register_virtio_driver+0x31/0x50
> >>>>>>     p9_virtio_init+0x3c/0x1000 [9pnet_virtio]
> >>>>>>     do_one_initcall+0x7b/0x380
> >>>>>>     do_init_module+0x5f/0x21e
> >>>>>>     load_module+0x265c/0x2c60
> >>>>>>     __do_sys_finit_module+0xb0/0xf0
> >>>>>>     __x64_sys_finit_module+0x1a/0x20
> >>>>>>     do_syscall_64+0x34/0xb0
> >>>>>>     entry_SYSCALL_64_after_hwframe+0x44/0xae
> >>>>>>
> >>>>>> When populating msi_irqs sysfs failed in msi_capability_init() or
> >>>>>> msix_capability_init(), dev->msi_irq_groups will point to ERR_PTR(...).
> >>>>>> This will cause a page fault when destroying the wrong
> >>>>>> dev->msi_irq_groups in free_msi_irqs().
> >>>>>>
> >>>>>> Fix this by setting dev->msi_irq_groups to NULL when msi_populate_sysfs()
> >>>>>> failed.
> >>>>>>
> >>>>>> Fixes: 2f170814bdd2 ("genirq/msi: Move MSI sysfs handling from PCI to MSI core")
> >>>>>> Reported-by: Hulk Robot <hulkci@...wei.com>
> >>> What exactly was reported by the Hulk Robot?  Did it really do the
> >>> fault injection and report the page fault?
> >> Yes, it reported the error and provided a way to reproduce it
> > Great, can you include a link to that report then?
> > .
> Currently hulk robot is still in the process of continuous improvement and
> is not open to the public for the time being, so you can not access our
> links at the moment. We will open it in the future when it is perfected.

hi hai, would you like to put some information in the commit log like
if  'msi_attrs = kcalloc() in msi_populate_sysfs()' fails, blah, blah, blah...

It seems this can make things a bit clearer to me. Anyway, it doesn't matter
too much. The fix is correct.

>
> --
> Wang Hai
>
Thanks
barry