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SubjectRe: [PATCH] irq/irq_domain: Quit ignoring error returns from irq_alloc_desc_from().
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
> 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.

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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