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SubjectRe: [PATCH] powerpc: powernv: Fix refcount leak bug in opal-powercap
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Le 17/06/2022 à 06:20, Liang He a écrit :
> In opal_powercap_init(), of_find_compatible_node() will return
> a node pointer with refcount incremented. We should use of_node_put()
> in fail path or when it is not used anymore.
>
> Besides, for_each_child_of_node() will automatically *inc* and *dec*
> refcount during iteration. However, we should add the of_node_put()
> if there is a break.

Hi,

I'm not sure that your patch is right here. Because of this *inc* and
*dec* things, do we still need to of_node_put(powercap) once we have
entered for_each_child_of_node?

I think that this reference will be released on the first iteration of
the loop.


Maybe of_node_put(powercap) should be duplicated everywhere it is
relevant and removed from the error handling path?
Or an additional reference should be taken before the loop?
Or adding a new label with "powercap = NULL" and branching there when
needed?

CJ

>
> Signed-off-by: Liang He <windhl@126.com>
> ---
> arch/powerpc/platforms/powernv/opal-powercap.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/opal-powercap.c b/arch/powerpc/platforms/powernv/opal-powercap.c
> index 64506b46e77b..b102477d3f95 100644
> --- a/arch/powerpc/platforms/powernv/opal-powercap.c
> +++ b/arch/powerpc/platforms/powernv/opal-powercap.c
> @@ -153,7 +153,7 @@ void __init opal_powercap_init(void)
> pcaps = kcalloc(of_get_child_count(powercap), sizeof(*pcaps),
> GFP_KERNEL);
> if (!pcaps)
> - return;
> + goto out_powercap;
>
> powercap_kobj = kobject_create_and_add("powercap", opal_kobj);
> if (!powercap_kobj) {
> @@ -236,6 +236,9 @@ void __init opal_powercap_init(void)
> kfree(pcaps[i].pg.name);
> }
> kobject_put(powercap_kobj);
> + of_node_put(node);
> out_pcaps:
> kfree(pcaps);
> +out_powercap:
> + of_node_put(powercap);
> }

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