linux-kernel - Re: [PATCH] iommu/intel: Fix memleak in intel_irq_remapping

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Date:   Sun, 3 Jan 2021 13:49:25 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     dinghao.liu@....edu.cn
Cc:     baolu.lu@...ux.intel.com, kjlu@....edu,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Jiang Liu <jiang.liu@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/intel: Fix memleak in intel_irq_remapping_alloc

On 2021/1/3 12:08, dinghao.liu@....edu.cn wrote:
>> Hi,
>>
>> On 2021/1/2 17:50, Dinghao Liu wrote:
>>> When irq_domain_get_irq_data() or irqd_cfg() fails
>>> meanwhile i == 0, data allocated by kzalloc() has not
>>> been freed before returning, which leads to memleak.
>>>
>>> Fixes: b106ee63abccb ("irq_remapping/vt-d: Enhance Intel IR driver to support hierarchical irqdomains")
>>> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
>>> ---
>>>    drivers/iommu/intel/irq_remapping.c | 2 ++
>>>    1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
>>> index aeffda92b10b..cdaeed36750f 100644
>>> --- a/drivers/iommu/intel/irq_remapping.c
>>> +++ b/drivers/iommu/intel/irq_remapping.c
>>> @@ -1354,6 +1354,8 @@ static int intel_irq_remapping_alloc(struct irq_domain *domain,
>>>    		irq_cfg = irqd_cfg(irq_data);
>>>    		if (!irq_data || !irq_cfg) {
>>>    			ret = -EINVAL;
>>> +			kfree(data);
>>> +			data = NULL;
>>
>> Do you need to check (i == 0) here? @data will not be used anymore as it
>> goes to out branch, why setting it to NULL here?
>>
> 
> data will be passed to ire_data->chip_data when i == 0 and
> intel_free_irq_resources() will free it on failure. Thus I

Isn't it going to "goto out_free_data"? If "i == 0", the allocated @data
won't be freed by intel_free_irq_resources(), hence memory leaking. Does
this patch aim to fix this?

Best regards,
baolu

> set it to NULL to prevent double-free. However, if we add
> a check (i == 0) here, we will not need to set it to NULL.
> If this is better, I will resend a new patch soon.
> 
> Regards,
> Dinghao
>