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SubjectRe: Re: [PATCH] iommu/intel: Fix memleak in intel_irq_remapping_alloc
> On 2021/1/3 12:08, dinghao.liu@zju.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@zju.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
>

Correct, this is what I mean. When i > 0, data has been passed to
irq_data->chip_data, which will be freed in intel_free_irq_resources()
on failure. So there is no memleak in this case. The memleak only occurs
on failure when i == 0 (data has not been passed to irq_data->chip_data).
I set data to NULL after kfree() in this patch to prevent double-free
when the failure occurs at i > 0.

Regards,
Dinghao

> > 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
> >
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