linux-kernel - Re: [PATCH 4.4 33/53] x86/apic/vector: Fix off by one in error path

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Date:   Sat, 17 Feb 2018 14:34:06 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ben Hutchings <ben.hutchings@...ethink.co.uk>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Keith Busch <keith.busch@...el.com>
Subject: Re: [PATCH 4.4 33/53] x86/apic/vector: Fix off by one in error
 path

On Fri, 16 Feb 2018, Ben Hutchings wrote:
> On Mon, 2018-01-22 at 09:40 +0100, Greg Kroah-Hartman wrote:
> > 4.4-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > From: Thomas Gleixner <tglx@...utronix.de>
> > 
> > commit 45d55e7bac4028af93f5fa324e69958a0b868e96 upstream.
> > 
> > Keith reported the following warning:
> > 
> > WARNING: CPU: 28 PID: 1420 at kernel/irq/matrix.c:222 irq_matrix_remove_managed+0x10f/0x120
> >   x86_vector_free_irqs+0xa1/0x180
> >   x86_vector_alloc_irqs+0x1e4/0x3a0
> >   msi_domain_alloc+0x62/0x130
> > 
> > The reason for this is that if the vector allocation fails the error
> > handling code tries to free the failed vector as well, which causes the
> > above imbalance warning to trigger.
> > 
> > Adjust the error path to handle this correctly.
> > 
> > Fixes: b5dc8e6c21e7 ("x86/irq: Use hierarchical irqdomain to manage CPU interrupt vectors")
> > Reported-by: Keith Busch <keith.busch@...el.com>
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > Tested-by: Keith Busch <keith.busch@...el.com>
> > Cc: stable@...r.kernel.org
> > Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801161217300.1823@nanos
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 
> > ---
> >  arch/x86/kernel/apic/vector.c |    7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > --- a/arch/x86/kernel/apic/vector.c
> > +++ b/arch/x86/kernel/apic/vector.c
> > @@ -359,14 +359,17 @@ static int x86_vector_alloc_irqs(struct
> >  		irq_data->chip_data = data;
> >  		irq_data->hwirq = virq + i;
> >  		err = assign_irq_vector_policy(virq + i, node, data, info);
> > -		if (err)
> > +		if (err) {
> > +			irq_data->chip_data = NULL;
> > +			free_apic_chip_data(data);
> >  			goto error;
> 
> This doesn't look quite right for 4.4.y (or any stable branch before
> 4.15.y).  When virq is a legacy IRQ this function doesn't allocate
> "data" and shouldn't free it.

Bah. I'm a moron. Lemme look at that.