Re: [PATCH V2] perf/x86/intel/uncore: Fix iounmap() leak on global_init failure

[Markus Elfring <Markus.Elfring@web.de>]

> Kernel test robot reported:

Is this duplicate information according to a known tag?


> Unverified Error/Warning (likely false positive, kindly check if
> interested):
>     arch/x86/events/intel/uncore_discovery.c:293:2-8:
>     ERROR: missing iounmap; ioremap on line 288 and execution via
>     conditional on line 292

See also:
https://elixir.bootlin.com/linux/v6.19-rc5/source/scripts/coccinelle/free/iounmap.cocci#L2-L8


> If domain->global_init() fails in __parse_discovery_table(), the
> ioremap'ed MMIO region is not released before returning, resulting
> in an MMIO mapping leak.
> 
> Reported-by: kernel test robot <lkp@intel.com>

See also once more:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.19-rc5#n94

Will another imperative wording approach become helpful for an improved change description?


…
> ---
>  arch/x86/events/intel/uncore_discovery.c | 15 ++++++++++-----
…

Some contributors would appreciate patch version descriptions.
https://lore.kernel.org/all/?q=%22This+looks+like+a+new+version+of+a+previously+submitted+patch%22
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.19-rc5#n310


Is there a need to perform desirable changes by a small patch series?

* Specific fix

* Related refinements


> +++ b/arch/x86/events/intel/uncore_discovery.c
> @@ -264,6 +264,7 @@ static int __parse_discovery_table(struct uncore_discovery_domain *domain,
>  	struct uncore_unit_discovery unit;
>  	void __iomem *io_addr;
>  	unsigned long size;
> +	int ret = 0;
>  	int i;

Would scope adjustments become helpful for any of these local variables?


> @@ -273,21 +274,23 @@ static int __parse_discovery_table(struct uncore_discovery_domain *domain,
>  
>  	/* Read Global Discovery State */
>  	memcpy_fromio(&global, io_addr, sizeof(struct uncore_global_discovery));
> +	iounmap(io_addr);
> +
>  	if (uncore_discovery_invalid_unit(global)) {
…
>  	}
> -	iounmap(io_addr);

Can this modification part be interpreted as an optimisation?


…
> -	if (domain->global_init && domain->global_init(global.ctl))
> -		return -ENODEV;
> +	if (domain->global_init && domain->global_init(global.ctl)) {
> +		ret = -ENODEV;
> +		goto out;
> +	}
…
>  	*parsed = true;
> +
> +out:

Would an other label be a bit clearer here?

unmap_io:

>  	iounmap(io_addr);
> -	return 0;
> +	return ret;
>  }
…


Regards,
Markus