linux-kernel - [PATCH 4.4 074/115] PCI/PME: Handle invalid data when reading Root Status

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Message-Id: <20171218152857.511958837@linuxfoundation.org>
Date:   Mon, 18 Dec 2017 16:49:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Qiang Zheng <zhengqiang10@...wei.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.4 074/115] PCI/PME: Handle invalid data when reading Root Status

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Qiang <zhengqiang10@...wei.com>

[ Upstream commit 3ad3f8ce50914288731a3018b27ee44ab803e170 ]

PCIe PME and native hotplug share the same interrupt number, so hotplug
interrupts are also processed by PME.  In some cases, e.g., a Link Down
interrupt, a device may be present but unreachable, so when we try to
read its Root Status register, the read fails and we get all ones data
(0xffffffff).

Previously, we interpreted that data as PCI_EXP_RTSTA_PME being set, i.e.,
"some device has asserted PME," so we scheduled pcie_pme_work_fn().  This
caused an infinite loop because pcie_pme_work_fn() tried to handle PME
requests until PCI_EXP_RTSTA_PME is cleared, but with the link down,
PCI_EXP_RTSTA_PME can't be cleared.

Check for the invalid 0xffffffff data everywhere we read the Root Status
register.

1469d17dd341 ("PCI: pciehp: Handle invalid data when reading from
non-existent devices") added similar checks in the hotplug driver.

Signed-off-by: Qiang Zheng <zhengqiang10@...wei.com>
[bhelgaas: changelog, also check in pcie_pme_work_fn(), use "~0" to follow
other similar checks]
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>

Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/pci/pcie/pme.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/pci/pcie/pme.c
+++ b/drivers/pci/pcie/pme.c
@@ -233,6 +233,9 @@ static void pcie_pme_work_fn(struct work
 			break;

 		pcie_capability_read_dword(port, PCI_EXP_RTSTA, &rtsta);
+		if (rtsta == (u32) ~0)
+			break;
+
 		if (rtsta & PCI_EXP_RTSTA_PME) {
 			/*
 			 * Clear PME status of the port.  If there are other
@@ -280,7 +283,7 @@ static irqreturn_t pcie_pme_irq(int irq,
 	spin_lock_irqsave(&data->lock, flags);
 	pcie_capability_read_dword(port, PCI_EXP_RTSTA, &rtsta);

-	if (!(rtsta & PCI_EXP_RTSTA_PME)) {
+	if (rtsta == (u32) ~0 || !(rtsta & PCI_EXP_RTSTA_PME)) {
 		spin_unlock_irqrestore(&data->lock, flags);
 		return IRQ_NONE;
 	}