x86/i8259: Mark legacy PIC interrupts with IRQ_LEVEL

commit 5fa55950729d0762a787451dc52862c3f850f859 upstream.

Baoquan reported that after triggering a crash the subsequent crash-kernel
fails to boot about half of the time. It triggers a NULL pointer
dereference in the periodic tick code.

This happens because the legacy timer interrupt (IRQ0) is resent in
software which happens in soft interrupt (tasklet) context. In this context
get_irq_regs() returns NULL which leads to the NULL pointer dereference.

The reason for the resend is a spurious APIC interrupt on the IRQ0 vector
which is captured and leads to a resend when the legacy timer interrupt is
enabled. This is wrong because the legacy PIC interrupts are level
triggered and therefore should never be resent in software, but nothing
ever sets the IRQ_LEVEL flag on those interrupts, so the core code does not
know about their trigger type.

Ensure that IRQ_LEVEL is set when the legacy PCI interrupts are set up.

Fixes: 1b9b99027512 ("[PATCH] genirq: add genirq sw IRQ-retrigger")
Reported-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Baoquan He <bhe@redhat.com>
Link: https://lore.kernel.org/r/87mt6rjrra.ffs@tglx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/i8259.c b/arch/x86/kernel/i8259.c
index fe522691ac717ff77347a68162c912d7b50edafb..8821d0ab0a08c3d0db72078cc7d82f7ebfbee368 100644 (file)
--- a/arch/x86/kernel/i8259.c
+++ b/arch/x86/kernel/i8259.c
@@ -114,6 +114,7 @@ static void make_8259A_irq(unsigned int irq)
        disable_irq_nosync(irq);
        io_apic_irqs &= ~(1<<irq);
        irq_set_chip_and_handler(irq, &i8259A_chip, handle_level_irq);
+       irq_set_status_flags(irq, IRQ_LEVEL);
        enable_irq(irq);
        lapic_assign_legacy_vector(irq, true);
 }

diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index 16919a9671fa93f89aac7ed279097898f6516b33..faed27c8dc39f9e0b239a6d6c5475a1f073a3f29 100644 (file)
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -72,8 +72,10 @@ void __init init_ISA_irqs(void)
 
        legacy_pic->init(0);
 
-       for (i = 0; i < nr_legacy_irqs(); i++)
+       for (i = 0; i < nr_legacy_irqs(); i++) {
                irq_set_chip_and_handler(i, chip, handle_level_irq);
+               irq_set_status_flags(i, IRQ_LEVEL);
+       }
 }
 
 void __init init_IRQ(void)