Re: [PATCH net v2] net: mdio-ipq4019: fix possible invalid pointer dereference

[Hui Tang]

On 2022/11/18 21:44, Andrew Lunn wrote:
> > So, the code should be as follows, is that right?
> >
> > +	void __iomem *devm_ioremap_resource_optional(struct device *dev,
> > +                                    	     const struct resource *res)
> > +	{
> > +		void __iomem *base;
> > +
> > +		base = __devm_ioremap_resource(dev, res, DEVM_IOREMAP);
> > +		if (IS_ERR(base) && PTR_ERR(base) == -ENOMEM)
> > +			return NULL;
> > +
> > +		return base;
> > +	}
> >
> >
> > [...]
> > 	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> > -	if (res)
> > +	if (res) {
> > +		priv->eth_ldo_rdy = devm_ioremap_resource_optional(&pdev->dev, res)
> > +		if (IS_ERR(priv->eth_ldo_rdy))
> > +			return PTR_ERR(priv->eth_ldo_rdy);
> > +	}
> > [...]
>
> Yes, that is the basic concept.
>
> The only thing i might change is the double meaning of -ENOMEM.
> __devm_ioremap_resource() allocates memory, and if that memory
> allocation fails, it returns -ENOMEM. If the resource does not exist,
> it also returns -ENOMEM. So you cannot tell these two error conditions
> apart. Most of the other get_foo() calls return -ENODEV if the
> gpio/regulator/clock does not exist, so you can tell if you are out of
> memory. But ioremap is specifically about memory so -ENOMEM actually
> makes sense.
>
> If you are out of memory, it seems likely the problem is not going to
> go away quickly, so the next allocation will also fail, and hopefully
> the error handling will then work. So i don't think it is major
> issue. So yes, go with the code above.

Hi, Andrew

My new patchset is ready, but I just found out that another patch has been
applied to netdev/net.git. Can I solve the problem in present way? And I
will add devm_ioremap_resource_optional() helper later to optimize related
drivers. How about this?

Thanks.