linux-kernel - Re: [PATCH] riscv: Prevent a bad reference count on CPU nodes

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Message-ID: <670535de.7b0a0220.311e0d.f680@mx.google.com>
Date: Tue, 08 Oct 2024 15:38:37 +0200
From: Miquel Sabaté Solà <mikisabate@...il.com>
To: paul.walmsley@...ive.com
Cc: palmer@...belt.com,  aou@...s.berkeley.edu,  cuiyunhui@...edance.com,
  sudeep.holla@....com,  jeremy.linton@....com,  sunilvl@...tanamicro.com,
  linux-riscv@...ts.infradead.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: Prevent a bad reference count on CPU nodes

On dl., de set. 30 2024, Miquel Sabaté Solà wrote:

> On dv., de set. 13 2024, Miquel Sabaté Solà wrote:
>
>> When populating cache leaves we previously fetched the CPU device node
>> at the very beginning. But when ACPI is enabled we go through a
>> specific branch which returns early and does not call 'of_node_put' for
>> the node that was acquired.
>>
>> Since we are not using a CPU device node for the ACPI code anyways, we
>> can simply move the initialization of it just passed the ACPI block, and
>> we are guaranteed to have an 'of_node_put' call for the acquired node.
>> This prevents a bad reference count of the CPU device node.
>>
>> Moreover, the previous function did not check for errors when acquiring
>> the device node, so a return -ENOENT has been added for that case.
>>
>> Signed-off-by: Miquel Sabaté Solà <mikisabate@...il.com>
>> ---
>> I was wondering if this should also be sent to stable, but  I have not seen
>> a report on it, and this is not responsible for an oops or anything like that.
>> So in the end I decided not to, but maybe you consider otherwise.
>>
>>  arch/riscv/kernel/cacheinfo.c | 7 +++++--
>>  1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/cacheinfo.c b/arch/riscv/kernel/cacheinfo.c
>> index d6c108c50cba..d32dfdba083e 100644
>> --- a/arch/riscv/kernel/cacheinfo.c
>> +++ b/arch/riscv/kernel/cacheinfo.c
>> @@ -75,8 +75,7 @@ int populate_cache_leaves(unsigned int cpu)
>>  {
>>  	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
>>  	struct cacheinfo *this_leaf = this_cpu_ci->info_list;
>> -	struct device_node *np = of_cpu_device_node_get(cpu);
>> -	struct device_node *prev = NULL;
>> +	struct device_node *np, *prev;
>>  	int levels = 1, level = 1;
>>
>>  	if (!acpi_disabled) {
>> @@ -100,6 +99,10 @@ int populate_cache_leaves(unsigned int cpu)
>>  		return 0;
>>  	}
>>
>> +	np = of_cpu_device_node_get(cpu);
>> +	if (!np)
>> +		return -ENOENT;
>> +
>>  	if (of_property_read_bool(np, "cache-size"))
>>  		ci_leaf_init(this_leaf++, CACHE_TYPE_UNIFIED, level);
>>  	if (of_property_read_bool(np, "i-cache-size"))
>
> Gently ping :)
>
> Could you take a look at this fix?
>
> Thanks,
> Miquel

Hello,

Would it make sense to have this fix for rc3?

Thanks,
Miquel

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