linux-kernel - Re: [PATCH v2] PCI: dwc: keystone: Fix potential NULL dereference

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Message-ID: <Zi9D4bWB9tDTXfHV@ryzen.lan>
Date: Mon, 29 Apr 2024 08:53:21 +0200
From: Niklas Cassel <cassel@...nel.org>
To: Aleksandr Mishin <amishin@...rgos.ru>
Cc: Rob Herring <robh@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Serge Semin <fancer.lancer@...il.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Damien Le Moal <dlemoal@...nel.org>,
	Siddharth Vadapalli <s-vadapalli@...com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH v2] PCI: dwc: keystone: Fix potential NULL dereference

On Thu, Apr 25, 2024 at 12:21:35PM +0300, Aleksandr Mishin wrote:
> In ks_pcie_setup_rc_app_regs() resource_list_first_type() may return
> NULL which is later dereferenced. Fix this bug by adding NULL check.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 0f71c60ffd26 ("PCI: dwc: Remove storing of PCI resources")
> Signed-off-by: Aleksandr Mishin <amishin@...rgos.ru>
> ---
> v2: Add return code processing
> 
>  drivers/pci/controller/dwc/pci-keystone.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-keystone.c b/drivers/pci/controller/dwc/pci-keystone.c
> index 844de4418724..5c6786d9f3e9 100644
> --- a/drivers/pci/controller/dwc/pci-keystone.c
> +++ b/drivers/pci/controller/dwc/pci-keystone.c
> @@ -382,17 +382,22 @@ static void ks_pcie_clear_dbi_mode(struct keystone_pcie *ks_pcie)
>  	} while (val & DBI_CS2);
>  }
>  
> -static void ks_pcie_setup_rc_app_regs(struct keystone_pcie *ks_pcie)
> +static int ks_pcie_setup_rc_app_regs(struct keystone_pcie *ks_pcie)
>  {
>  	u32 val;
>  	u32 num_viewport = ks_pcie->num_viewport;
>  	struct dw_pcie *pci = ks_pcie->pci;
>  	struct dw_pcie_rp *pp = &pci->pp;
> -	u64 start, end;
> +	struct resource_entry *ft;
>  	struct resource *mem;
> +	u64 start, end;
>  	int i;
>  
> -	mem = resource_list_first_type(&pp->bridge->windows, IORESOURCE_MEM)->res;
> +	ft = resource_list_first_type(&pp->bridge->windows, IORESOURCE_MEM);
> +	if (!ft)
> +		return -EINVAL;
> +
> +	mem = ft->res;
>  	start = mem->start;
>  	end = mem->end;
>  
> @@ -403,7 +408,7 @@ static void ks_pcie_setup_rc_app_regs(struct keystone_pcie *ks_pcie)
>  	ks_pcie_clear_dbi_mode(ks_pcie);
>  
>  	if (ks_pcie->is_am6)
> -		return;
> +		return 0;
>  
>  	val = ilog2(OB_WIN_SIZE);
>  	ks_pcie_app_writel(ks_pcie, OB_SIZE, val);
> @@ -420,6 +425,8 @@ static void ks_pcie_setup_rc_app_regs(struct keystone_pcie *ks_pcie)
>  	val = ks_pcie_app_readl(ks_pcie, CMD_STATUS);
>  	val |= OB_XLAT_EN_VAL;
>  	ks_pcie_app_writel(ks_pcie, CMD_STATUS, val);
> +
> +	return 0;
>  }
>  
>  static void __iomem *ks_pcie_other_map_bus(struct pci_bus *bus,
> @@ -814,7 +821,10 @@ static int __init ks_pcie_host_init(struct dw_pcie_rp *pp)
>  		return ret;
>  
>  	ks_pcie_stop_link(pci);
> -	ks_pcie_setup_rc_app_regs(ks_pcie);
> +	ret = ks_pcie_setup_rc_app_regs(ks_pcie);

Since ks_pcie_setup_rc_app_regs() returns 0 on success,
I suggest you do:

if (ret)
	return ret;

Instead.

> +	if (ret < 0)
> +		return ret;
> +


Kind regards,
Niklas