linux-kernel - Re: [PATCH] PCI: xgene-msi: Fix a potential UAF in xgene_msi

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Date:   Tue, 26 Sep 2023 10:21:13 +0800 (GMT+08:00)
From:   dinghao.liu@....edu.cn
To:     "Marc Zyngier" <maz@...nel.org>
Cc:     "Toan Le" <toan@...amperecomputing.com>,
        "Lorenzo Pieralisi" <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        "Rob Herring" <robh@...nel.org>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>, "Duc Dang" <dhdang@....com>,
        "Tanmay Inamdar" <tinamdar@....com>, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: xgene-msi: Fix a potential UAF in xgene_msi_probe

> On Mon, 25 Sep 2023 07:21:32 +0100,
> Dinghao Liu <dinghao.liu@....edu.cn> wrote:
> > 
> > xgene_allocate_domains() will call irq_domain_remove() to free
> > msi->inner_domain on failure. However, its caller, xgene_msi_probe(),
> > will also call irq_domain_remove() through xgene_msi_remove() on the
> > same failure, which may lead to a use-after-free. Set the freed pointer
> > to NULL to fix this issue.
> > 
> > Fixes: dcd19de36775 ("PCI: xgene: Add APM X-Gene v1 PCIe MSI/MSIX termination driver")
> > Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> > ---
> >  drivers/pci/controller/pci-xgene-msi.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/pci/controller/pci-xgene-msi.c b/drivers/pci/controller/pci-xgene-msi.c
> > index 3ce38dfd0d29..c0192c5ff0f3 100644
> > --- a/drivers/pci/controller/pci-xgene-msi.c
> > +++ b/drivers/pci/controller/pci-xgene-msi.c
> > @@ -253,6 +253,7 @@ static int xgene_allocate_domains(struct xgene_msi *msi)
> >  
> >  	if (!msi->msi_domain) {
> >  		irq_domain_remove(msi->inner_domain);
> > +		msi->inner_domain = NULL;
> >  		return -ENOMEM;
> >  	}
> 
> Why can't we just drop the irq_domain_remove() call here instead, and
> simply rely on xgene_msi_remove() to do the right thing? Something
> like the untested patch below.
> 
> Thanks,
> 
> 	M.
> 
> diff --git a/drivers/pci/controller/pci-xgene-msi.c b/drivers/pci/controller/pci-xgene-msi.c
> index 0234e528b9a5..f98c9eb7bebf 100644
> --- a/drivers/pci/controller/pci-xgene-msi.c
> +++ b/drivers/pci/controller/pci-xgene-msi.c
> @@ -251,10 +251,8 @@ static int xgene_allocate_domains(struct xgene_msi *msi)
>  						    &xgene_msi_domain_info,
>  						    msi->inner_domain);
>  
> -	if (!msi->msi_domain) {
> -		irq_domain_remove(msi->inner_domain);
> +	if (!msi->msi_domain)
>  		return -ENOMEM;
> -	}
>  
>  	return 0;
>  }

Thanks for your advice! This patch is more concise. I will resend a new patch soon.

Regards,
Dinghao