linux-kernel - Re: [PATCH] of: property: Add missing of_node_get() in parse

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Date:   Wed, 1 Mar 2023 10:29:19 +0100
From:   Jean-Jacques Hiblot <jjhiblot@...phandler.com>
To:     Saravana Kannan <saravanak@...gle.com>
CC:     <robh+dt@...nel.org>, <frowand.list@...il.com>,
        <gregkh@...uxfoundation.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH] of: property: Add missing of_node_get() in
 parse_interrupt()


On 28/02/2023 20:07, Saravana Kannan wrote:
> On Tue, Feb 28, 2023 at 9:40 AM Jean-Jacques Hiblot
> <jjhiblot@...phandler.com> wrote:
>> From: Jean Jacques Hiblot <jjhiblot@...phandler.com>
>>
>> As all the other parsers do, parse_interrupt() must increase the refcount
>> of the device_node. Otherwise the refcount is decremented every time
>> parse_interrupt() is called on this node, leading to a potential
>> use-after-free.
>>
>> This is a regression introduced by commit f265f06af194 ("of: property:
>> Fix fw_devlink handling of interrupts/interrupts-extended"). The reason is
>> that of_irq_parse_one() does not increase the refcount while the previously
>> used of_irq_find_parent() does.
> Thanks for catching the issue Jean!
>
> This feels like a bug in of_irq_parse_one() to me. It's returning a
> reference to a node without doing a of_node_get() on it.
>
> Rob, Marc, Do you agree?

Sarvana,

it looks like you're right. The bug seems to be in of_irq_parse_one().

It doesn't behave in the same way for "interrupts-extended" where it 
does a get() and 'interrupts" where it doesn't.

So please ignore this patch.

Thanks

>
> Jean,
>
> If they agree, can you please fix of_irq_parse_one() and add a
> of_node_put() to existing callers (if they aren't already doing a
> put()).
>
> Thanks,
> Saravana
>
>> Fixes: f265f06af194 ("of: property: Fix fw_devlink handling of interrupts/interrupts-extended")
>> Signed-off-by: Jean Jacques Hiblot <jjhiblot@...phandler.com>
>> ---
>>   drivers/of/property.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/of/property.c b/drivers/of/property.c
>> index 134cfc980b70b..1f23bcb765c4e 100644
>> --- a/drivers/of/property.c
>> +++ b/drivers/of/property.c
>> @@ -1380,7 +1380,10 @@ static struct device_node *parse_interrupts(struct device_node *np,
>>              strcmp(prop_name, "interrupts-extended"))
>>                  return NULL;
>>
>> -       return of_irq_parse_one(np, index, &sup_args) ? NULL : sup_args.np;
>> +       if (of_irq_parse_one(np, index, &sup_args))
>> +               return NULL;
>> +
>> +       return of_node_get(sup_args.np);
>>   }
>>
>>   static const struct supplier_bindings of_supplier_bindings[] = {
>> --
>> 2.25.1
>>