[patch 01/14] x86/irq: Fix a race in x86_vector_free_irqs()

[Thomas Gleixner <tglx@linutronix.de>]

[-- Attachment #1: x86-irq-fix-a-race-window-in-x86_vector_free_irqs.patch --]
[-- Type: text/plain, Size: 2980 bytes --]

There's a race condition between

x86_vector_free_irqs()
{
	free_apic_chip_data(irq_data->chip_data);
	xxxxx	//irq_data->chip_data has been freed, but the pointer
		//hasn't been reset yet
	irq_domain_reset_irq_data(irq_data);
}

and 

smp_irq_move_cleanup_interrupt()
{
	raw_spin_lock(&vector_lock);
	data = apic_chip_data(irq_desc_get_irq_data(desc));
	access data->xxxx	// may access freed memory
	raw_spin_unlock(&desc->lock);
}

which may cause smp_irq_move_cleanup_interrupt() to access freed memory.

Call irq_domain_reset_irq_data(), which clears the pointer with vector lock
held.

[ tglx: Free memory outside of lock held region. ]

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Jeremiah Mahler <jmmahler@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: andy.shevchenko@gmail.com
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Joe Lawrence <joe.lawrence@stratus.com>
Link: http://lkml.kernel.org/r/1450880014-11741-3-git-send-email-jiang.liu@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/apic/vector.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -224,10 +224,8 @@ static int assign_irq_vector_policy(int
 static void clear_irq_vector(int irq, struct apic_chip_data *data)
 {
 	struct irq_desc *desc;
-	unsigned long flags;
 	int cpu, vector;
 
-	raw_spin_lock_irqsave(&vector_lock, flags);
 	BUG_ON(!data->cfg.vector);
 
 	vector = data->cfg.vector;
@@ -237,10 +235,8 @@ static void clear_irq_vector(int irq, st
 	data->cfg.vector = 0;
 	cpumask_clear(data->domain);
 
-	if (likely(!data->move_in_progress)) {
-		raw_spin_unlock_irqrestore(&vector_lock, flags);
+	if (likely(!data->move_in_progress))
 		return;
-	}
 
 	desc = irq_to_desc(irq);
 	for_each_cpu_and(cpu, data->old_domain, cpu_online_mask) {
@@ -253,7 +249,6 @@ static void clear_irq_vector(int irq, st
 		}
 	}
 	data->move_in_progress = 0;
-	raw_spin_unlock_irqrestore(&vector_lock, flags);
 }
 
 void init_irq_alloc_info(struct irq_alloc_info *info,
@@ -274,19 +269,24 @@ void copy_irq_alloc_info(struct irq_allo
 static void x86_vector_free_irqs(struct irq_domain *domain,
 				 unsigned int virq, unsigned int nr_irqs)
 {
+	struct apic_chip_data *apic_data;
 	struct irq_data *irq_data;
+	unsigned long flags;
 	int i;
 
 	for (i = 0; i < nr_irqs; i++) {
 		irq_data = irq_domain_get_irq_data(x86_vector_domain, virq + i);
 		if (irq_data && irq_data->chip_data) {
+			raw_spin_lock_irqsave(&vector_lock, flags);
 			clear_irq_vector(virq + i, irq_data->chip_data);
-			free_apic_chip_data(irq_data->chip_data);
+			apic_data = irq_data->chip_data;
+			irq_domain_reset_irq_data(irq_data);
+			raw_spin_unlock_irqrestore(&vector_lock, flags);
+			free_apic_chip_data(apic_data);
 #ifdef	CONFIG_X86_IO_APIC
 			if (virq + i < nr_legacy_irqs())
 				legacy_irq_data[virq + i] = NULL;
 #endif
-			irq_domain_reset_irq_data(irq_data);
 		}
 	}
 }