[PATCH] powerpc/pseries: fix oops in hotplug memory notifier

[Michael Ellerman]

Nathan Lynch <nathanl at linux.ibm.com> writes:

> During post-migration device tree updates, we can oops in
> pseries_update_drconf_memory if the source device tree has an
> ibm,dynamic-memory-v2 property and the destination has a
> ibm,dynamic_memory (v1) property. The notifier processes an "update"
> for the ibm,dynamic-memory property but it's really an add in this
> scenario. So make sure the old property object is there before
> dereferencing it.
>
> Signed-off-by: Nathan Lynch <nathanl at linux.ibm.com>

Can you pinpoint a commit that introduced the bug? Should we backport
this to stable?

Perhaps?
  Fixes: 2b31e3aec1db ("powerpc/drmem: Add support for ibm, dynamic-memory-v2 property")

cheers

> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 47087832f8b2..e6bd172bcf30 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -980,6 +980,9 @@ static int pseries_update_drconf_memory(struct of_reconfig_data *pr)
>  	if (!memblock_size)
>  		return -EINVAL;
>  
> +	if (!pr->old_prop)
> +		return 0;
> +
>  	p = (__be32 *) pr->old_prop->value;
>  	if (!p)
>  		return -EINVAL;
> -- 
> 2.20.1