Re: [PATCH v1] x86: fix kernel crash on boot due to NULL dereference

[Andy Shevchenko]

On Fri, Jul 18, 2014 at 12:34 AM, David Cohen
<david.a.cohen@xxxxxxxxxxxxxxx> wrote:
> Hi Andy,
>
> Thanks for the patch.
>
> On Thu, Jul 17, 2014 at 05:59:41PM +0300, Andy Shevchenko wrote:
>> The patch "x86, irq: Count legacy IRQs by legacy_pic->nr_legacy_irqs instead of
>> NR_IRQS_LEGACY" (linux-next commit 95d76acc7518d566df18d67c1343bb375b78d1f3)
>> removed reserved interrupts for the platforms that do not have a legacy IOAPIC.
>> Meanwhile it breks a boot on Intel MID platforms such as Medfield.
>
> Have you tested it against Merrifield?

No, I have only Medfield device around me. If you can do that on
Merrifield I will appreciate your Tested-by tag.

>
> Br, David
>
>>
>> [    0.000000] BUG: unable to handle kernel NULL pointer dereference at 0000003a
>> [    0.000000] IP: [<c107079a>] setup_irq+0xf/0x4d
>> [    0.000000] *pdpt = 0000000000000000 *pde = 9bbf32453167e510
>> [    0.000000] Oops: 0000 [#1] PREEMPT SMP
>> [    0.000000] Modules linked in:
>> [    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.16.0-rc5-next-20140717-00043-g6ab7e8d-dirty #497
>> [    0.000000] task: c184bc80 ti: c183e000 task.ti: c183e000
>> [    0.000000] EIP: 0060:[<c107079a>] EFLAGS: 00210046 CPU: 0
>> [    0.000000] EIP is at setup_irq+0xf/0x4d
>> [    0.000000] EAX: 00000000 EBX: 00000002 ECX: 00000000 EDX: 00000002
>> [    0.000000] ESI: 000000d5 EDI: c184e280 EBP: c183ffc0 ESP: c183ffb4
>> [    0.000000]  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
>> [    0.000000] CR0: 8005003b CR2: 0000003a CR3: 0195b000 CR4: 000006b0
>> [    0.000000] Stack:
>> [    0.000000]  00000100 000000d5 c195c800 c183ffd0 c18eff07 c1935100 00010800 c183ffd8
>> [    0.000000]  c18efca0 c183ffe8 c18ec92e c1935100 00020800 c183fff8 c18ec2b4 00020800
>> [    0.000000]  c195c800 025e5003 00000000
>> [    0.000000] Call Trace:
>> [    0.000000]  [<c18eff07>] native_init_IRQ+0x265/0x273
>> [    0.000000]  [<c18efca0>] init_IRQ+0x2c/0x2e
>> [    0.000000]  [<c18ec92e>] start_kernel+0x1e4/0x32a
>> [    0.000000]  [<c18ec2b4>] i386_start_kernel+0x82/0x86
>> [    0.000000] Code: eb 05 bf ea ff ff ff 8b 83 c4 00 00 00 e8 f6 a3 01 00 8d 65 f4 89 f8 5b 5e 5f 5d c3 55 89 e5 57 89 d7 56 53 89 c3 e8 4b e4 ff ff <f6> 40 3a 02 89 c6 74 16 b8 2b 3e 77 c1 ba 0a 05 00 00 e8 83 60
>> [    0.000000] EIP: [<c107079a>] setup_irq+0xf/0x4d SS:ESP 0068:c183ffb4
>> [    0.000000] CR2: 000000000000003a
>> [    0.000000] ---[ end trace cb88537fdc8fa200 ]---
>> [    0.000000] Kernel panic - not syncing: Attempted to kill the idle task!
>> [    0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task!
>>
>> The culprit is an uncoditional setting of the IRQ2 which is used as cascade IRQ
>> on legacy platforms. It seems we have to check if we have enough legacy IRQs
>> reserved before we can call setup_irq().
>>
>> The proposed patch adds such check.
>>
>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
>> ---
>>  arch/x86/kernel/irqinit.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
>> index 1e6cff5..44f1ed4 100644
>> --- a/arch/x86/kernel/irqinit.c
>> +++ b/arch/x86/kernel/irqinit.c
>> @@ -203,7 +203,7 @@ void __init native_init_IRQ(void)
>>               set_intr_gate(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);
>>       }
>>
>> -     if (!acpi_ioapic && !of_ioapic)
>> +     if (!acpi_ioapic && !of_ioapic && nr_legacy_irqs())
>>               setup_irq(2, &irq2);
>>
>>  #ifdef CONFIG_X86_32
>> --
>> 2.0.1
>>
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-- 
With Best Regards,
Andy Shevchenko
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