linux-kernel - Re: [tpmdd-devel] [PATCH] tpm_crb: fix bad name pointer usage with struct resource

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Message-ID: <20160217045219.GA26086@obsidianresearch.com>
Date:	Tue, 16 Feb 2016 21:52:19 -0700
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:	Peter Huewe <peterhuewe@....de>, tpmdd-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [tpmdd-devel] [PATCH] tpm_crb: fix bad name pointer usage with
 struct resource

On Wed, Feb 17, 2016 at 02:27:54AM +0200, Jarkko Sakkinen wrote:
> -	if (acpi_dev_resource_memory(ares, &res))
> +	if (acpi_dev_resource_memory(ares, &res)) {
> +		res.name = NULL;

What? How is this not a bug in acpi_dev_resource_memory? Maybe it
needs to memcpy into devm allocated memory instead, but I'm confused
how/why/when acpi could free name.

The same code exists in tpm_tis as well.

>  {
> -	struct resource new_res = {
> -		.start	= start,
> -		.end	= start + size - 1,
> -		.flags	= IORESOURCE_MEM,
> -	};
> +	struct resource new_res;
> +
> +	memset(&new_res, 0, sizeof(new_res));
> +
> +	new_res.start	= start;
> +	new_res.end	= start + size - 1;
> +	new_res.flags	= IORESOURCE_MEM;

These two things are equivalent (C requires non-initialized members of
an initalized struct to be 0), why this change?

Jason