Re: [PATCH] x86: irq: Check for valid irq descriptor in check_irq_vectors_for_cpu_disable

[Joerg Roedel]

Hi Jiang,

On Thu, Feb 05, 2015 at 01:51:26PM +0800, Jiang Liu wrote:
> Reviewed-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>

Thanks for your review.

> Actually there's another racing pattern.
> for (irq = 0; irq < nr_irqs; irq++) {
> 	desc = irq_to_desc(irq);
> 	access desc->xxx
> }
> 
> When sparsing IRQ is enabled, there's no mechanism to protect
> desc returned by irq_to_desc(). Once I have considered a brute
> solution of disabling freeing of irq_desc:(

Hmm, how about wrapping the places that use irq_desc in rcu_read_lock()
and do a synchronize_rcu() before we free it (at least in the SPARSE_IRQ
case)? It wouldn't be a real RCU data structure, but we make at least
sure that we don't free an irq_desc thats in use.


	Joerg

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/