This is a note to let you know that I've just added the patch titled x86/ioapic: Prevent NULL pointer dereference in setup_ioapic_dest() to the 4.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-ioapic-prevent-null-pointer-dereference-in-setup_ioapic_dest.patch and it can be found in the queue-4.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From ababae44108b0e94b58eef6cb5bd830bd040a47f Mon Sep 17 00:00:00 2001 From: Werner Pawlitschko <werner.pawlitschko@xxxxxxxx> Date: Tue, 27 Oct 2015 09:08:04 +0900 Subject: x86/ioapic: Prevent NULL pointer dereference in setup_ioapic_dest() From: Werner Pawlitschko <werner.pawlitschko@xxxxxxxx> commit ababae44108b0e94b58eef6cb5bd830bd040a47f upstream. 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 <tglx@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/apic/io_apic.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- 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 Patches currently in stable-queue which might be from werner.pawlitschko@xxxxxxxx are queue-4.2/x86-ioapic-prevent-null-pointer-dereference-in-setup_ioapic_dest.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html