linux-kernel - Re: [PATCH] PCI: pciehp: Prevent child devices from doing RPM on PCIe Link Down

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Date:   Tue, 17 Oct 2023 09:13:57 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     bhelgaas@...gle.com, linux-pm@...r.kernel.org,
        linux-mmc@...r.kernel.org, Ricky Wu <ricky_wu@...ltek.com>,
        Kees Cook <keescook@...omium.org>,
        Tony Luck <tony.luck@...el.com>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: pciehp: Prevent child devices from doing RPM on
 PCIe Link Down

[cc -= unrelated mailing lists bpf, kernel-hardening]

On Tue, Oct 17, 2023 at 12:35:18PM +0800, Kai-Heng Feng wrote:
> On Mon, Oct 16, 2023 at 5:32???PM Lukas Wunner <lukas@...ner.de> wrote:
> > On Mon, Oct 16, 2023 at 12:01:31PM +0800, Kai-Heng Feng wrote:
> > > [   63.898861] pcieport 0000:00:1c.0: pciehp: Slot(8): Link Down
> > > [   63.912118] BUG: unable to handle page fault for address: ffffb24d403e5010
> > [...]
> > > [   63.912198]  ? asm_exc_page_fault+0x27/0x30
> > > [   63.912203]  ? ioread32+0x2e/0x70
> > > [   63.912206]  ? rtsx_pci_write_register+0x5b/0x90 [rtsx_pci]
> > > [   63.912217]  rtsx_set_l1off_sub+0x1c/0x30 [rtsx_pci]
> > > [   63.912226]  rts5261_set_l1off_cfg_sub_d0+0x36/0x40 [rtsx_pci]
> > > [   63.912234]  rtsx_pci_runtime_idle+0xc7/0x160 [rtsx_pci]
> > > [   63.912243]  ? __pfx_pci_pm_runtime_idle+0x10/0x10
> > > [   63.912246]  pci_pm_runtime_idle+0x34/0x70
> > > [   63.912248]  rpm_idle+0xc4/0x2b0
> > > [   63.912251]  pm_runtime_work+0x93/0xc0
> > > [   63.912254]  process_one_work+0x21a/0x430
> > > [   63.912258]  worker_thread+0x4a/0x3c0
> >
> > This looks like pcr->remap_addr is accessed after it has been iounmap'ed
> > in rtsx_pci_remove() or before it has been iomap'ed in rtsx_pci_probe().
> >
> > Is the card reader itself located below a hotplug port and unplugged here?
> > Or is this about the card being removed from the card reader?
> >
> > Having full dmesg output and lspci -vvv output attached to a bugzilla
> > would help to understand what is going on.
> 
> I don't have the hardware so we need Ricky to provide more information here.
> 
> Regardless of the cardreader issue, do you have any concern on the patch
> itself?

Yes, my concern is that this might be the wrong approach.  I would like
to understand what is going on, hence my questions above.

Thanks,

Lukas