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

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Date: Tue, 17 Oct 2023 05:44:13 +0000
From: Ricky WU <ricky_wu@...ltek.com>
To: Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Lukas Wunner
	<lukas@...ner.de>
CC: "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-pm@...r.kernel.org"
	<linux-pm@...r.kernel.org>,
        "linux-mmc@...r.kernel.org"
	<linux-mmc@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>, Tony Luck
	<tony.luck@...el.com>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>
Subject: RE: [PATCH] PCI: pciehp: Prevent child devices from doing RPM on PCIe Link Down



> -----Original Message-----
> From: Kai-Heng Feng <kai.heng.feng@...onical.com>
> 
> 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:
> > > When inserting an SD7.0 card to Realtek card reader, it can trigger
> > > PCI slot Link down and causes the following error:
> >
> > Why does *inserting* a card cause a Link Down?
> 
> Ricky, do you know the reason why Link Down happens?
> 

Because SD7.0 card is use pcie-nvme driver, reader need to re-link then just do the pcie channel 

> >
> >
> > > [   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?
> 
> Kai-Heng
> 
> >
> > Thanks,
> >
> > Lukas