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SubjectRe: [PATCH] irq/irq_domain: Quit ignoring error returns from irq_alloc_desc_from().
On 04/06/2012 11:37 AM, David Daney wrote:
> Rob,
>
> What the he*%? ...
>
>
> On 04/05/2012 08:37 PM, Rob Herring wrote:
>> On 04/05/2012 06:52 PM, David Daney wrote:
>>> From: David Daney<david.daney@cavium.com>
>>>
>>> In commit 4bbdd45a (irq_domain/powerpc: eliminate irq_map; use
>>> irq_alloc_desc() instead) code was added that ignores error returns
>>> from irq_alloc_desc_from() by (silently) casting the return value to
>>> unsigned. The negitive value error return now suddenly looks like a
>>> valid irq number.
>>>
>>> Commits cc79ca69 (irq_domain: Move irq_domain code from powerpc to
>>> kernel/irq) and 1bc04f2c (irq_domain: Add support for base irq and
>>> hwirq in legacy mappings) move this code to its current location in
>
> That would be commits:
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=4bbdd45afdae208a7c4ade89cf602f89a6397cff
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=cc79ca691c292e9fd44f589c7940b9654e22f2f6
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=1bc04f2cf8c2a1feadbd994f50c40bb145bf2989
>
>
>>> irqdomain.c
>>>
>>> The result of all of this is a null pointer dereference OOPS if one of
>>> the error cases is hit.
>>>
>>> The fix: Don't cast away the negativeness of the return value and then
>>> check for errors.
>>>
>>> Signed-off-by: David Daney<david.daney@cavium.com>
>>> ---
>>> kernel/irq/irqdomain.c | 11 ++++++-----
>>> 1 files changed, 6 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
>>> index af48e59..9d3e3ae 100644
>>> --- a/kernel/irq/irqdomain.c
>>> +++ b/kernel/irq/irqdomain.c
>>> @@ -351,6 +351,7 @@ unsigned int irq_create_mapping(struct irq_domain
>>> *domain,
>>> irq_hw_number_t hwirq)
>>> {
>>> unsigned int virq, hint;
>>> + int irq;
>>>
>>> pr_debug("irq: irq_create_mapping(0x%p, 0x%lx)\n", domain, hwirq);
>>>
>>> @@ -380,14 +381,14 @@ unsigned int irq_create_mapping(struct
>>> irq_domain *domain,
>>> hint = hwirq % irq_virq_count;
>>> if (hint == 0)
>>> hint++;
>>> - virq = irq_alloc_desc_from(hint, 0);
>>
>> You are not looking at mainline. hint was removed in later versions, and
>> the referenced commit ids don't exist.
>
> Please look at Linus' tree before making incorrect statements about
> whether or not code exists on the 'mainline'
>
> The current kernel.org tree contains the bug and will cause anything
> using irq_create_mapping() to crash in a semi-random manner.
>

Doh, evidently I need git training... Sorry about that. I was looking at
a 3.2 branch even though I did check that. Plus I was remembering Grant
removed some of the hint code in later versions of the irq domain code.

My only comment is perhaps the pr_debug should be an error msg unless
you get an error message already. Otherwise, FWIW:

Acked-by: Rob Herring <rob.herring@calxeda.com>

Off to find my brain,
Rob


> David Daney
>
>>
>> Rob
>>
>>> - if (!virq)
>>> - virq = irq_alloc_desc_from(1, 0);
>>> - if (!virq) {
>>> + irq = irq_alloc_desc_from(hint, 0);
>>> + if (irq<= 0)
>>> + irq = irq_alloc_desc_from(1, 0);
>>> + if (irq<= 0) {
>>> pr_debug("irq: -> virq allocation failed\n");
>>> return 0;
>>> }
>>> -
>>> + virq = irq;
>>> if (irq_setup_virq(domain, virq, hwirq)) {
>>> if (domain->revmap_type != IRQ_DOMAIN_MAP_LEGACY)
>>> irq_free_desc(virq);
>>
>>
>



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