2021-06-21 15:52:52

by Colin King

Subject: re: stmmac: pci: Add dwmac support for Loongson

Hi,

Static analysis by Coverity on today's linux-next has found an issue in
function loongson_dwmac_probe with the following commit:

commit 30bba69d7db40e732d6c0aa6d4890c60d717e314
Author: Qing Zhang <[email protected]>
Date: Fri Jun 18 10:53:34 2021 +0800

stmmac: pci: Add dwmac support for Loongson

The analysis is as follows:

110 plat->phy_interface = device_get_phy_mode(&pdev->dev);

Enum compared against 0
(NO_EFFECT)
unsigned_compare: This less-than-zero comparison of an
unsigned value is never true. plat->phy_interface < 0U.

111 if (plat->phy_interface < 0)
112 dev_err(&pdev->dev, "phy_mode not found\n");

Enum plat->phy_interface is unsigned, so can't be negative and so the
comparison will always be false.

A possible fix is to use int variable ret for the assignment and check:


ret = device_get_phy_mode(&pdev->dev);
if (ret < 0)
dev_err(&pdev->dev, "phy_mode not found\n");
plat->phy_interface = ret;

..however, I think the dev_err may need handling too, e.g.

ret = device_get_phy_mode(&pdev->dev);
if (ret < 0) {
dev_err(&pdev->dev, "phy_mode not found\n");
ret = -ENODEV;
goto cleanup; /* needs to be written */
}
plat->phy_interface = ret;

Colin

2021-06-21 16:55:38

by Andrew Lunn

Subject: Re: stmmac: pci: Add dwmac support for Loongson

On Mon, Jun 21, 2021 at 04:51:28PM +0100, Colin Ian King wrote:
> Hi,
>
> Static analysis by Coverity on today's linux-next has found an issue in
> function loongson_dwmac_probe with the following commit:
>
> commit 30bba69d7db40e732d6c0aa6d4890c60d717e314
> Author: Qing Zhang <[email protected]>
> Date: Fri Jun 18 10:53:34 2021 +0800
>
> stmmac: pci: Add dwmac support for Loongson
>
> The analysis is as follows:
>
> 110 plat->phy_interface = device_get_phy_mode(&pdev->dev);
>
> Enum compared against 0
> (NO_EFFECT)
> unsigned_compare: This less-than-zero comparison of an
> unsigned value is never true. plat->phy_interface < 0U.
>
> 111 if (plat->phy_interface < 0)
> 112 dev_err(&pdev->dev, "phy_mode not found\n");
>
> Enum plat->phy_interface is unsigned, so can't be negative and so the
> comparison will always be false.
>
> A possible fix is to use int variable ret for the assignment and check:
>
>
> ret = device_get_phy_mode(&pdev->dev);
> if (ret < 0)
> dev_err(&pdev->dev, "phy_mode not found\n");
> plat->phy_interface = ret;
>
> ..however, I think the dev_err may need handling too, e.g.
>
> ret = device_get_phy_mode(&pdev->dev);
> if (ret < 0) {
> dev_err(&pdev->dev, "phy_mode not found\n");
> ret = -ENODEV;
> goto cleanup; /* needs to be written */
> }
> plat->phy_interface = ret;

Potentially a cleaner fix is to use of_get_phy_mode(), which separates
the success/error value from the phy_interface_t.

Andrew

2021-06-22 02:19:13

by Qing Zhang

Subject: Re: stmmac: pci: Add dwmac support for Loongson

On 06/21/2021 11:51 PM, Colin Ian King wrote:
> Hi,
>
> Static analysis by Coverity on today's linux-next has found an issue in
> function loongson_dwmac_probe with the following commit:
>
> commit 30bba69d7db40e732d6c0aa6d4890c60d717e314
> Author: Qing Zhang <[email protected]>
> Date: Fri Jun 18 10:53:34 2021 +0800
>
> stmmac: pci: Add dwmac support for Loongson
>
> The analysis is as follows:
>
> 110 plat->phy_interface = device_get_phy_mode(&pdev->dev);
>
> Enum compared against 0
> (NO_EFFECT)
> unsigned_compare: This less-than-zero comparison of an
> unsigned value is never true. plat->phy_interface < 0U.
>
> 111 if (plat->phy_interface < 0)
> 112 dev_err(&pdev->dev, "phy_mode not found\n");
>
> Enum plat->phy_interface is unsigned, so can't be negative and so the
> comparison will always be false.

Hi，Colin

Thanks for your advice,

I see this judgment in stmmac_platform.c:

plat->phy_interface = device_get_phy_mode(&pdev->dev);
if (plat->phy_interface < 0)
return ERR_PTR(plat->phy_interface);

plat->interface = stmmac_of_get_mac_mode(np);
if (plat->interface < 0)

>
> A possible fix is to use int variable ret for the assignment and check:
>
>
> ret = device_get_phy_mode(&pdev->dev);
> if (ret < 0)
> dev_err(&pdev->dev, "phy_mode not found\n");
> plat->phy_interface = ret;
>
> ..however, I think the dev_err may need handling too, e.g.
>
> ret = device_get_phy_mode(&pdev->dev);
> if (ret < 0) {
> dev_err(&pdev->dev, "phy_mode not found\n");
> ret = -ENODEV;
> goto cleanup; /* needs to be written */
> }
> plat->phy_interface = ret;
>
> Colin
looks ok, but can be written to use of_get_phy_mode() , like this:

phy_interface_t interface;
ret = of_get_phy_mode(pdev->dev->of_node, &interface);
if (ret)
return -EINVAL;


plat_dat->interface = interface;
if(!plat->interface)
dev_err(&pdev->dev, "Unsupported interface mode: %s",
phy_modes(plat->interface));

Thanks

-Qing