From: Dimitri Sivanich Date: Tue, 16 Oct 2012 12:50:21 +0000 (-0500) Subject: x86/irq/ioapic: Check for valid irq_cfg pointer in smp_irq_move_cleanup_interrupt X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=94777fc51b3ad85ff9f705ddf7cdd0eb3bbad5a6;p=openwrt%2Fstaging%2Fblogic.git x86/irq/ioapic: Check for valid irq_cfg pointer in smp_irq_move_cleanup_interrupt Posting this patch to fix an issue concerning sparse irq's that I raised a while back. There was discussion about adding refcounting to sparse irqs (to fix other potential race conditions), but that does not appear to have been addressed yet. This covers the only issue of this type that I've encountered in this area. A NULL pointer dereference can occur in smp_irq_move_cleanup_interrupt() if we haven't yet setup the irq_cfg pointer in the irq_desc.irq_data.chip_data. In create_irq_nr() there is a window where we have set vector_irq in __assign_irq_vector(), but not yet called irq_set_chip_data() to set the irq_cfg pointer. Should an IRQ_MOVE_CLEANUP_VECTOR hit the cpu in question during this time, smp_irq_move_cleanup_interrupt() will attempt to process the aforementioned irq, but panic when accessing irq_cfg. Only continue processing the irq if irq_cfg is non-NULL. Signed-off-by: Dimitri Sivanich Cc: Suresh Siddha Cc: Joerg Roedel Cc: Yinghai Lu Cc: Alexander Gordeev Link: http://lkml.kernel.org/r/20121016125021.GA22935@sgi.com Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index c265593ec2cd..1817fa911024 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -2257,6 +2257,9 @@ asmlinkage void smp_irq_move_cleanup_interrupt(void) continue; cfg = irq_cfg(irq); + if (!cfg) + continue; + raw_spin_lock(&desc->lock); /*