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

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Message-ID: <20120521211917.GA25567@sgi.com>
Date:	Mon, 21 May 2012 16:19:17 -0500
From:	Dimitri Sivanich <sivanich@....com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	x86@...nel.org, Suresh Siddha <suresh.b.siddha@...el.com>,
	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, May 21, 2012 at 11:07:04PM +0200, Thomas Gleixner wrote:
> On Mon, 21 May 2012, 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.
> 
> It seems that you either missed or failed to explain why it should be
> done _after_ taking the lock.
> 
> Changelogs matter, really.
>
How about this?


The smp_irq_move_cleanup_interrupt routine should be checking for a valid
irq_cfg pointer prior to accessing it.

Follow the same protocol shown in irq_set_chip_data(), by taking the desc
lock before accessing this location.

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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