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

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Date: Mon, 16 Oct 2023 11:32:10 +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,
	linux-hardening@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH] PCI: pciehp: Prevent child devices from doing RPM on
 PCIe Link Down

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?


> [   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.

Thanks,

Lukas