linux-kernel - Re: [patch 00/14] x86/irq: Plug various vector cleanup races

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Date:	Thu, 14 Jan 2016 09:24:35 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Joe Lawrence <joe.lawrence@...atus.com>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Peter Anvin <hpa@...or.com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Jeremiah Mahler <jmmahler@...il.com>,
	Borislav Petkov <bp@...en8.de>, andy.shevchenko@...il.com,
	Guenter Roeck <linux@...ck-us.net>
Subject: Re: [patch 00/14] x86/irq: Plug various vector cleanup races

On Mon, 4 Jan 2016, Joe Lawrence wrote:
> No issues running the same PCI device removal and stress tests against
> the patchset.

Thanks for testing!

Though there is yet another long standing bug in that area. Fix below.

Thanks,

	tglx

8<--------------------

Subject: x86/irq: Call chip->irq_set_affinity in proper context
From: Thomas Gleixner <tglx@...utronix.de>
Date: Thu, 14 Jan 2016 08:43:38 +0100

setup_ioapic_dest() calls irqchip->irq_set_affinity() completely
unprotected. That's wrong in several aspects:

 - it triggers a lockdep splat because vector lock is taken with interrupts
   enabled.

 - it opens a race window where irq_set_affinity() can be interrupted and the
   irq chip left in unconsistent state.

The proper calling convention is irq descriptor lock held and interrupts
disabled.

Reported-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: stable@...r.kernel.org
---
 arch/x86/kernel/apic/io_apic.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2521,6 +2521,7 @@ void __init setup_ioapic_dest(void)
 {
 	int pin, ioapic, irq, irq_entry;
 	const struct cpumask *mask;
+	struct irq_desc *desc;
 	struct irq_data *idata;
 	struct irq_chip *chip;
 
@@ -2536,7 +2537,9 @@ void __init setup_ioapic_dest(void)
 		if (irq < 0 || !mp_init_irq_at_boot(ioapic, irq))
 			continue;
 
-		idata = irq_get_irq_data(irq);
+		desc = irq_to_desc(irq);
+		raw_spin_lock_irq(d&desc->lock);
+		idata = irq_desc_get_irq_data(desc);
 
 		/*
 		 * Honour affinities which have been set in early boot
@@ -2550,6 +2553,7 @@ void __init setup_ioapic_dest(void)
 		/* Might be lapic_chip for irq 0 */
 		if (chip->irq_set_affinity)
 			chip->irq_set_affinity(idata, mask, false);
+		raw_spin_unlock_irq(d&desc->lock);
 	}
 }
 #endif