x86/irq: Plug vector setup race

Hogan reported a vector setup race, which overwrites the interrupt
descriptor in the per CPU vector array resulting in a disfunctional device.

CPU0				CPU1
				interrupt is raised in APIC IRR
				but not handled
  free_irq()
    per_cpu(vector_irq, CPU1)[vector] = VECTOR_SHUTDOWN;

  request_irq()			common_interrupt()
  				  d = this_cpu_read(vector_irq[vector]);

    per_cpu(vector_irq, CPU1)[vector] = desc;

    				  if (d == VECTOR_SHUTDOWN)
				    this_cpu_write(vector_irq[vector], VECTOR_UNUSED);

free_irq() cannot observe the pending vector in the CPU1 APIC as there is
no way to query the remote CPUs APIC IRR.

This requires that request_irq() uses the same vector/CPU as the one which
was freed, but this also can be triggered by a spurious interrupt.

Interestingly enough this problem managed to be hidden for more than a
decade.

Prevent this by reevaluating vector_irq under the vector lock, which is
held by the interrupt activation code when vector_irq is updated.

To avoid ifdeffery or IS_ENABLED() nonsense, move the
[un]lock_vector_lock() declarations out under the
CONFIG_IRQ_DOMAIN_HIERARCHY guard as it's only provided when
CONFIG_X86_LOCAL_APIC=y.

The current CONFIG_IRQ_DOMAIN_HIERARCHY guard is selected by
CONFIG_X86_LOCAL_APIC, but can also be selected by other parts of the
Kconfig system, which makes 32-bit UP builds with CONFIG_X86_LOCAL_APIC=n
fail.

Can we just get rid of this !APIC nonsense once and forever?

Fixes: 9345005f4eed ("x86/irq: Fix do_IRQ() interrupt warning for cpu hotplug retriggered irqs")
Reported-by: Hogan Wang <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Hogan Wang <[email protected]>
Link: https://lore.kernel.org/all/draft-87ikjhrhhh.ffs@tglx

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index 162ebd73a698..cbe19e669080 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -92,8 +92,6 @@ struct irq_cfg {
 
 extern struct irq_cfg *irq_cfg(unsigned int irq);
 extern struct irq_cfg *irqd_cfg(struct irq_data *irq_data);
-extern void lock_vector_lock(void);
-extern void unlock_vector_lock(void);
 #ifdef CONFIG_SMP
 extern void vector_schedule_cleanup(struct irq_cfg *);
 extern void irq_complete_move(struct irq_cfg *cfg);
@@ -101,12 +99,16 @@ extern void irq_complete_move(struct irq_cfg *cfg);
 static inline void vector_schedule_cleanup(struct irq_cfg *c) { }
 static inline void irq_complete_move(struct irq_cfg *c) { }
 #endif
-
 extern void apic_ack_edge(struct irq_data *data);
-#else	/*  CONFIG_IRQ_DOMAIN_HIERARCHY */
+#endif /* CONFIG_IRQ_DOMAIN_HIERARCHY */
+
+#ifdef CONFIG_X86_LOCAL_APIC
+extern void lock_vector_lock(void);
+extern void unlock_vector_lock(void);
+#else
 static inline void lock_vector_lock(void) {}
 static inline void unlock_vector_lock(void) {}
-#endif	/* CONFIG_IRQ_DOMAIN_HIERARCHY */
+#endif
 
 /* Statistics */
 extern atomic_t irq_err_count;