On Sun, 1 Nov 2015, Greg KH wrote:
> On Sun, Nov 01, 2015 at 07:26:28PM +0100, Marc Haber wrote:
> > Hi,
> >
> > On Sat, Oct 31, 2015 at 03:23:45PM -0700, Greg KH wrote:
> > > On Sat, Oct 31, 2015 at 10:15:51PM +0100, Marc Haber wrote:
> > > > I run a PC Engines APU in my basement for local infrastructure with
> > > > KVM. Kernels 4.2.4 and 4.2.5 panic on bootup pretty fast after the
> > > > usual "x86: Booted up 1 node, 2 CPUs", "smpboot: Total of 2 processors
> > > > activated (3999.89 BogoMIPS)" message. The message I would expect
> > > > instead of the kernel panic would be "devtmpfs: initialized", as one
> > > > can see on a successful 4.2.3 boot with identical kernel configuration.
> > >
> > > If you use 'git bisect' between 4.2.3 and 4.2.5, can you find the
> > > problem commit for us to help track this down?
> >
> > The winner is ...
> > [21f751a634f3b5eaf916f940e47f327fbc6e9727] x86/ioapic: Force affinity setting in setup_ioapic_dest()
> >
> > After rolling this back in 4.2.5, the APU now runs fine.
>
> Ok, this matches up with commit 21f751a634f3b5eaf916f940e47f327fbc6e9727
> in Linus's tree.
>
> Thomas and Mika, any thoughts about this?
>
> Marc, do you have this same problem with Linus's tree at the moment as
> well?
I just sent a pull request to Linus with a fix for this. Patch below.
Thanks,
tglx
---
commit ababae44108b0e94b58eef6cb5bd830bd040a47f
Author: Werner Pawlitschko <werner.pawlitschko@xxxxxxxx>
Date: Tue Oct 27 09:08:04 2015 +0900
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 <tglx@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
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
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