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Date: Tue, 10 Apr 2012 14:41:53 -0600 From: Grant Likely <grant.likely@...retlab.ca> To: David Daney <ddaney.cavm@...il.com> Cc: David Daney <ddaney.cavm@...il.com>, devicetree-discuss@...ts.ozlabs.org, Rob Herring <rob.herring@...xeda.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Thomas Gleixner <tglx@...utronix.de>, linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] irq/irq_domain: Quit ignoring error returns from irq_alloc_desc_from(). On Mon, 09 Apr 2012 09:56:30 -0700, David Daney <ddaney.cavm@...il.com> wrote: > On 04/06/2012 06:26 PM, Grant Likely wrote: > > On Thu, 5 Apr 2012 16:52:13 -0700, David Daney<ddaney.cavm@...il.com> wrote: > >> From: David Daney<david.daney@...ium.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@...ium.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; > > > > Merged, but I've dropped the new variable in favour of making virq an > > int. Makes for a smaller diffstat. > > > > Thanks Grant, > > I had thought about that too, but since virq throughout all the rest of > the code is unsigned, I didn't want to introduce an inconsistency. > > After a little more thought, I think that the domain of virq and the irq > used by the rest of the kernel are the same, so it might make sense to > change virq to be int universally, and use the kernel convention that > negative numbers indicate error conditions. But that would be a much > larger patch. ... touching pretty much *every* driver in the kernel! Blech! Yeah, that's not going to happen. As a rule, irq numbers are always unsigned, but there are a few apis that can return either '0' meaning no irq, or a negative value indicating an error. The irq_alloc_desc apis unfortunately are one such case. g. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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