Commit 9ae05225 authored Mar 06, 2020 by Thomas Gleixner

PCI/AER: Fix the broken interrupt injection

The AER error injection mechanism just blindly abuses generic_handle_irq()
which is really not meant for consumption by random drivers. The include of
linux/irq.h should have been a red flag in the first place. Driver code,
unless implementing interrupt chips or low level hypervisor functionality
has absolutely no business with that.

Invoking generic_handle_irq() from non interrupt handling context can have
nasty side effects at least on x86 due to the hardware trainwreck which
makes interrupt affinity changes a fragile beast. Sathyanarayanan triggered
a NULL pointer dereference in the low level APIC code that way. While the
particular pointer could be checked this would only paper over the issue
because there are other ways to trigger warnings or silently corrupt state.

Invoke the new irq_inject_interrupt() mechanism, which has the necessary
sanity checks in place and injects the interrupt via the irq_retrigger()
mechanism, which is at least halfways safe vs. the fragile x86 affinity
change mechanics.

It's safe on x86 as it does not corrupt state, but it still can cause a
premature completion of an interrupt affinity change causing the interrupt
line to become stale. Very unlikely, but possible.

For regular operations this is a non issue as AER error injection is meant
for debugging and testing and not for usage on production systems. People
using this should better know what they are doing.

Fixes: 390e2db8 ("PCI/AER: Abstract AER interrupt handling")
Reported-by: <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lkml.kernel.org/r/20200306130624.098374457@linutronix.de

parent acd26bcf

drivers/pci/pcie/Kconfig

+1 −0

Original line number	Diff line number	Diff line
		@@ -34,6 +34,7 @@ config PCIEAER
		config PCIEAER_INJECT
		tristate "PCI Express error injection support"
		depends on PCIEAER
		select GENERIC_IRQ_INJECTION
		help
		This enables PCI Express Root Port Advanced Error Reporting
		(AER) software error injector.

drivers/pci/pcie/aer_inject.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -16,7 +16,7 @@

		#include <linux/module.h>
		#include <linux/init.h>
		#include <linux/irq.h>
		#include <linux/interrupt.h>
		#include <linux/miscdevice.h>
		#include <linux/pci.h>
		#include <linux/slab.h>
		@@ -468,9 +468,7 @@ static int aer_inject(struct aer_error_inj *einj)
		}
		pci_info(edev->port, "Injecting errors %08x/%08x into device %s\n",
		einj->cor_status, einj->uncor_status, pci_name(dev));
		local_irq_disable();
		generic_handle_irq(edev->irq);
		local_irq_enable();
		ret = irq_inject_interrupt(edev->irq);
		} else {
		pci_err(rpdev, "AER device not found\n");
		ret = -ENODEV;

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