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

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Date:   Sun, 3 Jan 2021 12:08:31 +0800 (GMT+08:00)
From:   dinghao.liu@....edu.cn
To:     "Lu Baolu" <baolu.lu@...ux.intel.com>
Cc:     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: Re: [PATCH] iommu/intel: Fix memleak in
 intel_irq_remapping_alloc

> 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
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