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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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