From ababae44108b0e94b58eef6cb5bd830bd040a47f Mon Sep 17 00:00:00 2001 From: Werner Pawlitschko Date: Tue, 27 Oct 2015 09:08:04 +0900 Subject: [PATCH] x86/ioapic: Prevent NULL pointer dereference in setup_ioapic_dest() Commit 4857c91f0d19 changed the way how irq affinity is setup in setup_ioapic_dest() from using the core helper function to unconditionally calling the irq_set_affinity() callback of the underlying irq chip. That results in a NULL pointer dereference for the rare case where the underlying irq chip is lapic_chip which has no irq_set_affinity() callback. lapic_chip is occasionally used for the timer interrupt (irq 0). The fix is simple: Check the availability of the callback instead of calling it unconditionally. Fixes: 4857c91f0d19 "x86/ioapic: Force affinity setting in setup_ioapic_dest()" Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org --- arch/x86/kernel/apic/io_apic.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index bb6bfc01cb82..4f2821527014 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -2547,7 +2547,9 @@ void __init setup_ioapic_dest(void) mask = apic->target_cpus(); chip = irq_data_get_irq_chip(idata); - chip->irq_set_affinity(idata, mask, false); + /* Might be lapic_chip for irq 0 */ + if (chip->irq_set_affinity) + chip->irq_set_affinity(idata, mask, false); } } #endif -- 2.11.0