linux-kernel - Re: [PATCH 03/11] PCI: of_property: Sanitize 32 bit PCI address parsed from DT

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Message-ID: <20240821152441.GA222583@bhelgaas>
Date: Wed, 21 Aug 2024 10:24:41 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Andrea della Porta <andrea.porta@...e.com>
Cc: Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Derek Kiernan <derek.kiernan@....com>,
	Dragan Cvetic <dragan.cvetic@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Saravana Kannan <saravanak@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org, netdev@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-arch@...r.kernel.org,
	Lee Jones <lee@...nel.org>, Andrew Lunn <andrew@...n.ch>,
	Stefan Wahren <wahrenst@....net>
Subject: Re: [PATCH 03/11] PCI: of_property: Sanitize 32 bit PCI address
 parsed from DT

On Tue, Aug 20, 2024 at 04:36:05PM +0200, Andrea della Porta wrote:
> The of_pci_set_address() function parse devicetree PCI range specifier

s/parse/parses/ ? 

> assuming the address is 'sanitized' at the origin, i.e. without checking
> whether the incoming address is 32 or 64 bit has specified in the flags.
> In this way an address with no OF_PCI_ADDR_SPACE_MEM64 set in the flagss

s/flagss/flags/

> could leak through and the upper 32 bits of the address will be set too,
> and this violates the PCI specs stating that ion 32 bit address the upper

s/ion/in/

> bit should be zero.

I don't understand this code, so I'm probably missing something.  It
looks like the interesting path here is:

  of_pci_prop_ranges
    res = &pdev->resource[...];
    for (j = 0; j < num; j++) {
      val64 = res[j].start;
      of_pci_set_address(..., val64, 0, flags, false);
 +      if (OF_PCI_ADDR_SPACE_MEM64)
 +        prop[1] = upper_32_bits(val64);
 +      else
 +        prop[1] = 0;

OF_PCI_ADDR_SPACE_MEM64 tells us about the size of the PCI bus
address, but the address (val64) is a CPU physical address, not a PCI
bus address, so I don't understand why of_pci_set_address() should use
OF_PCI_ADDR_SPACE_MEM64 to clear part of the CPU address.

Add blank lines between paragraphs.

> This could cause mapping translation mismatch on PCI devices (e.g. RP1)
> that are expected to be addressed with a 64 bit address while advertising
> a 32 bit address in the PCI config region.
> Add a check in of_pci_set_address() to set upper 32 bits to zero in case
> the address has no 64 bit flag set.

Is this an indication of a DT error?  Have you seen this cause a
problem?  If so, what does it look like to a user?  I.e., how could a
user find this patch if they saw a problem?

> Signed-off-by: Andrea della Porta <andrea.porta@...e.com>
> ---
>  drivers/pci/of_property.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/of_property.c b/drivers/pci/of_property.c
> index 5a0b98e69795..77865facdb4a 100644
> --- a/drivers/pci/of_property.c
> +++ b/drivers/pci/of_property.c
> @@ -60,7 +60,10 @@ static void of_pci_set_address(struct pci_dev *pdev, u32 *prop, u64 addr,
>  	prop[0] |= flags | reg_num;
>  	if (!reloc) {
>  		prop[0] |= OF_PCI_ADDR_FIELD_NONRELOC;
> -		prop[1] = upper_32_bits(addr);
> +		if (FIELD_GET(OF_PCI_ADDR_FIELD_SS, flags) == OF_PCI_ADDR_SPACE_MEM64)
> +			prop[1] = upper_32_bits(addr);
> +		else
> +			prop[1] = 0;
>  		prop[2] = lower_32_bits(addr);
>  	}
>  }
> -- 
> 2.35.3
>