linux-kernel - Re: [PATCH v4] PCI: Relabel JHL6540 on Lenovo X1 Carbon 7,8

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Date: Sat, 27 Apr 2024 17:09:34 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Esther Shimanovich <eshimanovich@...omium.org>
Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Mario Limonciello <mario.limonciello@....com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Rajat Jain <rajatja@...gle.com>
Subject: Re: [PATCH v4] PCI: Relabel JHL6540 on Lenovo X1 Carbon 7,8

On Thu, Apr 25, 2024 at 05:16:24PM -0400, Esther Shimanovich wrote:
> I did find one example of a docking station that uses the DSL6540
> chip, which has PCI IDs defined in include/linux/pci_ids.h:
> #define PCI_DEVICE_ID_INTEL_ALPINE_RIDGE_4C_NHI     0x1577
> #define PCI_DEVICE_ID_INTEL_ALPINE_RIDGE_4C_BRIDGE  0x1578
> It seems like it has an NHI, despite being in an external, removable
> docking station.

Could you provide full output of dmesg and lspci -vvv of a machine
with this docking station attached?

Perhaps open a bug at bugzilla.kernel.org and attach it there?

Could you then try the below patch and see if it prevents the
Thunderbolt driver from binding to the hot-plugged device?

Thanks!

-- >8 --
>From a10a294a650232c16447a43c2b591f34d3cb399f Mon Sep 17 00:00:00 2001
From: Lukas Wunner <lukas@...ner.de>
Date: Sat, 27 Apr 2024 16:24:18 +0200
Subject: [PATCH] thunderbolt: Do not bind to NHI exposed by a hot-plugged
 device

An NHI should only be exposed by Thunderbolt host controllers, not by
hot-plugged devices.

Avoid binding to an NHI erroneously or maliciously exposed by a device
by looking at the upstream port of its switch:

On a host controller, the upstream port is of type TB_TYPE_NHI, whereas
on hot-plugged devices it is of type TB_TYPE_PORT.

Signed-off-by: Lukas Wunner <lukas@...ner.de>
Cc: stable@...r.kernel.org
---
 drivers/thunderbolt/tb.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index e00e62de53f3..d95ff9ed4d96 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -2786,6 +2786,13 @@ static int tb_start(struct tb *tb, bool reset)
 	if (IS_ERR(tb->root_switch))
 		return PTR_ERR(tb->root_switch);
 
+	/* NHI erroneously exposed by a hot-plugged device? */
+	if (!tb_port_is_nhi(tb_upstream_port(tb->root_switch))) {
+		tb_err(tb, "not a host controller\n");
+		tb_switch_put(tb->root_switch);
+		return -ENODEV;
+	}
+
 	/*
 	 * ICM firmware upgrade needs running firmware and in native
 	 * mode that is not available so disable firmware upgrade of the
-- 
2.43.0