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

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Date:   Fri, 16 Feb 2018 20:57:41 +0000
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Cc:     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 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.

Ben.

> +		}
>  	}
>  
>  	return 0;
>  
>  error:
> -	x86_vector_free_irqs(domain, virq, i + 1);
> +	x86_vector_free_irqs(domain, virq, i);
>  	return err;
>  }
>  
> 
> 
> 
-- 
Ben Hutchings
Software Developer, Codethink Ltd.