Re: [tip:x86/core 1/1] vmlinux.o: warning: objtool: rcar_pcie_probe+0x13e: no-cfi indirect call!

[Kees Cook]

On Fri, Oct 10, 2025 at 03:30:12PM -0700, Nathan Chancellor wrote:
> On Fri, Oct 10, 2025 at 09:44:46AM +0200, Peter Zijlstra wrote:
> > That's here... and that is indeed broken. Also note how it zeros r11
> > right before calling it.
> > 
> > AFAICT this is:
> > 
> >         host->phy_init_fn = of_device_get_match_data(dev);
> >         err = host->phy_init_fn(host);
> > 
> > Where it has decided that of_device_get_match_data() *will* return NULL
> > and then helpfully emits (*NULL)(); or something like that. And then
> 
> Oh duh because it will :)
> 
>   $ rg '^(# )?CONFIG_OF' .config
>   1528:# CONFIG_OF is not set
> 
> which means that of_device_get_match_data() is always NULL:
> 
>   static inline const void *of_device_get_match_data(const struct device *dev)
>   {
>       return NULL;
>   }
> 
> > forgets to add CFI bits on for extra fun and games.
> 
> which means this is another instance of what Sami mentioned happening on
> another report of a similar issue
> 
>   https://lore.kernel.org/CABCJKue1wCB6jBLYUc-fAEzpyQWHXwbk8R5GBaZCkCao0EQZPA@xxxxxxxxxxxxxx/
> 
> which does somewhat make sense because what's the point of setting up
> the CFI call if you know nothing can actually make use of it since we
> will crash when trying to indirectly call a NULL pointer?
> 
> Something like this would avoid this issue then.
> 
> Cheers,
> Nathan
> 
> diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c
> index 213028052aa5..15514c9c1927 100644
> --- a/drivers/pci/controller/pcie-rcar-host.c
> +++ b/drivers/pci/controller/pcie-rcar-host.c
> @@ -981,7 +981,7 @@ static int rcar_pcie_probe(struct platform_device *pdev)
>  		goto err_clk_disable;
>  
>  	host->phy_init_fn = of_device_get_match_data(dev);
> -	err = host->phy_init_fn(host);
> +	err = host->phy_init_fn ? host->phy_init_fn(host) : -ENODEV;
>  	if (err) {
>  		dev_err(dev, "failed to init PCIe PHY\n");
>  		goto err_clk_disable;

Much preferred over "always crash" ;) Nice digging!

Reviewed-by: Kees Cook <kees@xxxxxxxxxx>

-- 
Kees Cook