[PATCH v2] irqchip/gic-v3-its: Fix double free on error

[PATCH v2] irqchip/gic-v3-its: Fix double free on error

[Guanrui Huang]

In its_vpe_irq_domain_alloc, when its_vpe_init() returns an error
with i > 0, its_vpe_irq_domain_free may free bitmap and vprop_page,
and then there is a double free in its_vpe_irq_domain_alloc.

Fix it by calling its_vpe_irq_domain_free directly, bitmap and
vprop_page will be freed in this function.

And check whether its_vm is equal to domain->host_data to make sure
its_vpe_irq_domain_free handle right its_vm.

Signed-off-by: Guanrui Huang <guanrui.huang@linux.alibaba.com>
---
 drivers/irqchip/irq-gic-v3-its.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index fca888b36680..72c44e555c88 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -4523,6 +4523,9 @@ static int its_vpe_irq_domain_alloc(struct irq_domain *domain, unsigned int virq
 
 	BUG_ON(!vm);
 
+	if (vm != domain->host_data)
+		return -EINVAL;
+
 	bitmap = its_lpi_alloc(roundup_pow_of_two(nr_irqs), &base, &nr_ids);
 	if (!bitmap)
 		return -ENOMEM;
@@ -4561,13 +4564,8 @@ static int its_vpe_irq_domain_alloc(struct irq_domain *domain, unsigned int virq
 		irqd_set_resend_when_in_progress(irq_get_irq_data(virq + i));
 	}
 
-	if (err) {
-		if (i > 0)
-			its_vpe_irq_domain_free(domain, virq, i);
-
-		its_lpi_free(bitmap, base, nr_ids);
-		its_free_prop_table(vprop_page);
-	}
+	if (err)
+		its_vpe_irq_domain_free(domain, virq, i);
 
 	return err;
 }
-- 
2.36.1


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Re: [PATCH v2] irqchip/gic-v3-its: Fix double free on error

[Marc Zyngier]

On Thu, 11 Apr 2024 11:56:30 +0100,
Guanrui Huang <guanrui.huang@linux.alibaba.com> wrote:
> 
> In its_vpe_irq_domain_alloc, when its_vpe_init() returns an error
> with i > 0, its_vpe_irq_domain_free may free bitmap and vprop_page,
> and then there is a double free in its_vpe_irq_domain_alloc.
> 
> Fix it by calling its_vpe_irq_domain_free directly, bitmap and
> vprop_page will be freed in this function.
> 
> And check whether its_vm is equal to domain->host_data to make sure
> its_vpe_irq_domain_free handle right its_vm.
> 
> Signed-off-by: Guanrui Huang <guanrui.huang@linux.alibaba.com>
> ---
>  drivers/irqchip/irq-gic-v3-its.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index fca888b36680..72c44e555c88 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -4523,6 +4523,9 @@ static int its_vpe_irq_domain_alloc(struct irq_domain *domain, unsigned int virq
>  
>  	BUG_ON(!vm);
>  
> +	if (vm != domain->host_data)
> +		return -EINVAL;
> +

How can this happen?

>  	bitmap = its_lpi_alloc(roundup_pow_of_two(nr_irqs), &base, &nr_ids);
>  	if (!bitmap)
>  		return -ENOMEM;
> @@ -4561,13 +4564,8 @@ static int its_vpe_irq_domain_alloc(struct irq_domain *domain, unsigned int virq
>  		irqd_set_resend_when_in_progress(irq_get_irq_data(virq + i));
>  	}
>  
> -	if (err) {
> -		if (i > 0)
> -			its_vpe_irq_domain_free(domain, virq, i);
> -
> -		its_lpi_free(bitmap, base, nr_ids);
> -		its_free_prop_table(vprop_page);
> -	}
> +	if (err)
> +		its_vpe_irq_domain_free(domain, virq, i);
>  
>  	return err;
>  }

This otherwise looks reasonable.

Thanks,

	M.

-- 
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Re: [PATCH v2] irqchip/gic-v3-its: Fix double free on error

[Guanrui Huang]

if (vm != domain->host_data)

This is just a safety check. It looks unlikely happened.
After all, vm is obtained from the args. If the caller has a bug, can we check here to avoid possible problems that may arise in later code?

Thanks,
Guanrui

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Re: [PATCH v2] irqchip/gic-v3-its: Fix double free on error

[Marc Zyngier]

On Thu, 11 Apr 2024 12:58:05 +0100,
Guanrui Huang <guanrui.huang@linux.alibaba.com> wrote:
> 
> if (vm != domain->host_data)
> 
> This is just a safety check. It looks unlikely happened.

It's not a safety check. It is just papering over problems. If you
don't trust the vm pointer, why do you trust the domain pointer? Why
do you trust *anything* at all?

> After all, vm is obtained from the args. If the caller has a bug,
> can we check here to avoid possible problems that may arise in later
> code?

If the caller has a bug, please fix the caller. Don't paper over it.

And you can remove the BUG_ON(!vm) which is equally useless.

Thanks,

	M.

-- 
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