[PATCH] arm/xen: Fix refcount leak in xen_dt_guest_init

[PATCH] arm/xen: Fix refcount leak in xen_dt_guest_init

[Miaoqian Lin]

The of_find_compatible_node() function returns a node pointer with
refcount incremented, We should use of_node_put() on it when done
Add the missing of_node_put() to release the refcount.

Fixes: 9b08aaa3199a ("ARM: XEN: Move xen_early_init() before efi_init()")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
---
 arch/arm/xen/enlighten.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index ec5b082f3de6..262f45f686b6 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -424,6 +424,7 @@ static void __init xen_dt_guest_init(void)
 
 	if (of_address_to_resource(xen_node, GRANT_TABLE_INDEX, &res)) {
 		pr_err("Xen grant table region is not found\n");
+		of_node_put(xen_node);
 		return;
 	}
 	xen_grant_frames = res.start;
-- 
2.17.1


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Re: [PATCH] arm/xen: Fix refcount leak in xen_dt_guest_init

[Stefano Stabellini]

On Wed, 9 Mar 2022, Miaoqian Lin wrote:
> The of_find_compatible_node() function returns a node pointer with
> refcount incremented, We should use of_node_put() on it when done
> Add the missing of_node_put() to release the refcount.
> 
> Fixes: 9b08aaa3199a ("ARM: XEN: Move xen_early_init() before efi_init()")
> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>

Thanks for the patch!


> ---
>  arch/arm/xen/enlighten.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index ec5b082f3de6..262f45f686b6 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -424,6 +424,7 @@ static void __init xen_dt_guest_init(void)
>  
>  	if (of_address_to_resource(xen_node, GRANT_TABLE_INDEX, &res)) {
>  		pr_err("Xen grant table region is not found\n");
> +		of_node_put(xen_node);
>  		return;
>  	}

This is adding a call to of_node_put on the error path. Shouldn't it
be called also in the non-error path?

Also, there is another instance of of_address_to_resource being called
in this file (in arch_xen_unpopulated_init), does it make sense to call
of_node_put there too?

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Re: [PATCH] arm/xen: Fix refcount leak in xen_dt_guest_init

[Miaoqian Lin]

Hi,

On Fri, Mar 11, 2022 at 06:01:11PM -0800, Stefano Stabellini wrote:
> On Wed, 9 Mar 2022, Miaoqian Lin wrote:
> > The of_find_compatible_node() function returns a node pointer with
> > refcount incremented, We should use of_node_put() on it when done
> > Add the missing of_node_put() to release the refcount.
> > 
> > Fixes: 9b08aaa3199a ("ARM: XEN: Move xen_early_init() before efi_init()")
> > Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
> 
> Thanks for the patch!
> 
> 
> > ---
> >  arch/arm/xen/enlighten.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > index ec5b082f3de6..262f45f686b6 100644
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -424,6 +424,7 @@ static void __init xen_dt_guest_init(void)
> >  
> >  	if (of_address_to_resource(xen_node, GRANT_TABLE_INDEX, &res)) {
> >  		pr_err("Xen grant table region is not found\n");
> > +		of_node_put(xen_node);
> >  		return;
> >  	}
> 
> This is adding a call to of_node_put on the error path. Shouldn't it
> be called also in the non-error path?

You're right. It should be called also in the non-error path.
I made a mistake.

> Also, there is another instance of of_address_to_resource being called
> in this file (in arch_xen_unpopulated_init), does it make sense to call
> of_node_put there too?

I think so, becase device node pointer np is a local variable.
So the reference it taken should be released in the scope.

I look into the whole codebase for this kind of usage pattern
($ret=of_find_compatible_node();of_address_to_resource($ret,_,_), 
$ret is a local variable), Most of them call of_node_put() when done. 
And document of of_find_compatible_node() also mentions
> Return: A node pointer with refcount incremented, use
> of_node_put() on it when done.

But I am not sure, Since I am unfamiliar with other code logic.
It better if the developers could double check. I found some 
similar cases in arch/arm. 

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[PATCH v2] arm/xen: Fix some refcount leaks

[Miaoqian Lin]

The of_find_compatible_node() function returns a node pointer with
refcount incremented, We should use of_node_put() on it when done
Add the missing of_node_put() to release the refcount.

Fixes: 9b08aaa3199a ("ARM: XEN: Move xen_early_init() before efi_init()")
Fixes: b2371587fe0c ("arm/xen: Read extended regions from DT and init Xen resource")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
---
changes in v2:
- call of_node_put in non-error path in xen_dt_guest_init
- fix same refcount leak error in arch_xen_unpopulated_init
---
 arch/arm/xen/enlighten.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index ec5b082f3de6..07eb69f9e7df 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -337,12 +337,15 @@ int __init arch_xen_unpopulated_init(struct resource **res)
 
 	if (!nr_reg) {
 		pr_err("No extended regions are found\n");
+		of_node_put(np);
 		return -EINVAL;
 	}
 
 	regs = kcalloc(nr_reg, sizeof(*regs), GFP_KERNEL);
-	if (!regs)
+	if (!regs) {
+		of_node_put(np);
 		return -ENOMEM;
+	}
 
 	/*
 	 * Create resource from extended regions provided by the hypervisor to be
@@ -403,8 +406,8 @@ int __init arch_xen_unpopulated_init(struct resource **res)
 	*res = &xen_resource;
 
 err:
+	of_node_put(np);
 	kfree(regs);
-
 	return rc;
 }
 #endif
@@ -424,8 +427,10 @@ static void __init xen_dt_guest_init(void)
 
 	if (of_address_to_resource(xen_node, GRANT_TABLE_INDEX, &res)) {
 		pr_err("Xen grant table region is not found\n");
+		of_node_put(xen_node);
 		return;
 	}
+	of_node_put(xen_node);
 	xen_grant_frames = res.start;
 }
 
-- 
2.17.1


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Re: [PATCH v2] arm/xen: Fix some refcount leaks

[Stefano Stabellini]

On Wed, 20 Apr 2022, Miaoqian Lin wrote:
> The of_find_compatible_node() function returns a node pointer with
> refcount incremented, We should use of_node_put() on it when done
> Add the missing of_node_put() to release the refcount.
> 
> Fixes: 9b08aaa3199a ("ARM: XEN: Move xen_early_init() before efi_init()")
> Fixes: b2371587fe0c ("arm/xen: Read extended regions from DT and init Xen resource")
> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

Juergen,  Boris,
I applied the patch to for-linus-5.18


> ---
> changes in v2:
> - call of_node_put in non-error path in xen_dt_guest_init
> - fix same refcount leak error in arch_xen_unpopulated_init
> ---
>  arch/arm/xen/enlighten.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index ec5b082f3de6..07eb69f9e7df 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -337,12 +337,15 @@ int __init arch_xen_unpopulated_init(struct resource **res)
>  
>  	if (!nr_reg) {
>  		pr_err("No extended regions are found\n");
> +		of_node_put(np);
>  		return -EINVAL;
>  	}
>  
>  	regs = kcalloc(nr_reg, sizeof(*regs), GFP_KERNEL);
> -	if (!regs)
> +	if (!regs) {
> +		of_node_put(np);
>  		return -ENOMEM;
> +	}
>  
>  	/*
>  	 * Create resource from extended regions provided by the hypervisor to be
> @@ -403,8 +406,8 @@ int __init arch_xen_unpopulated_init(struct resource **res)
>  	*res = &xen_resource;
>  
>  err:
> +	of_node_put(np);
>  	kfree(regs);
> -
>  	return rc;
>  }
>  #endif
> @@ -424,8 +427,10 @@ static void __init xen_dt_guest_init(void)
>  
>  	if (of_address_to_resource(xen_node, GRANT_TABLE_INDEX, &res)) {
>  		pr_err("Xen grant table region is not found\n");
> +		of_node_put(xen_node);
>  		return;
>  	}
> +	of_node_put(xen_node);
>  	xen_grant_frames = res.start;
>  }
>  
> -- 
> 2.17.1
> 

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