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

Ben Hutchings
2018-02-16T20:57:45Z

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@linutronix.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@intel.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Tested-by: Keith Busch <keith.busch@intel.com>
> Cc: stable@vger.kernel.org
> Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801161217300.1823@nanos
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.