linux-kernel - Re: [PATCH] x86: check for valid irq_cfg pointer in smp_irq_move_cleanup

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Message-ID: <1337634353.1997.144.camel@sbsiddha-desk.sc.intel.com>
Date:	Mon, 21 May 2012 14:05:53 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Dimitri Sivanich <sivanich@....com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Yinghai Lu <yinghai@...nel.org>,
	Naga Chumbalkar <nagananda.chumbalkar@...com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: check for valid irq_cfg pointer in
 smp_irq_move_cleanup_interrupt

On Mon, 2012-05-21 at 11:49 -0500, Dimitri Sivanich wrote:
> The smp_irq_move_cleanup_interrupt routine should be checking for a valid
> irq_cfg pointer prior to accessing it.  It also seems that this should be
> done after taking the desc lock.

I think these changes are correct. Did you see any crashes during module
unload etc?

Reviewed-by: Suresh Siddha <suresh.b.siddha@...el.com>

> 
> Signed-off-by: Dimitri Sivanich <sivanich@....com>
> ---
>  arch/x86/kernel/apic/io_apic.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> Index: linux/arch/x86/kernel/apic/io_apic.c
> ===================================================================
> --- linux.orig/arch/x86/kernel/apic/io_apic.c
> +++ linux/arch/x86/kernel/apic/io_apic.c
> @@ -2478,9 +2478,12 @@ asmlinkage void smp_irq_move_cleanup_int
>  		if (!desc)
>  			continue;
>  
> -		cfg = irq_cfg(irq);
>  		raw_spin_lock(&desc->lock);
>  
> +		cfg = irq_cfg(irq);
> +		if (!cfg)
> +			goto unlock;
> +
>  		/*
>  		 * Check if the irq migration is in progress. If so, we
>  		 * haven't received the cleanup request yet for this irq.


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