linux-kernel - Re: [patch] firmware: qemu_fw_cfg.c: potential unintialized variable

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Date:	Thu, 14 Apr 2016 22:12:53 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	"Gabriel L. Somlo" <somlo@....edu>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>, qemu-devel@...gnu.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [patch] firmware: qemu_fw_cfg.c: potential unintialized variable

On Thu, Apr 14, 2016 at 02:40:06PM -0400, Gabriel L. Somlo wrote:
> On Thu, Apr 14, 2016 at 12:33:37PM +0300, Dan Carpenter wrote:
> > It acpi_acquire_global_lock() return AE_NOT_CONFIGURED then "glk" isn't
>   ^                               ^
>   If                            returns
> 
> > initialized, which, if you got very unlucky, could cause a bug.
> 
> 
> In principle I'm OK with being cautious and initializing local
> variables just in case, but I'm curious:
> 
> acpi_acquire_global_lock() (and its friend, acpi_release_global_lock())
> are both wrapped inside the same macro -- ACPI_HW_DEPENDENT_RETURN_STATUS
> -- which either makes them both do something useful, or makes them both
> no-ops returning a hardcoded AE_NOT_CONFIGURED.
> 
> So what else do you think could be a way to get very unlucky ?

If "glk" happened to to equal acpi_gbl_global_lock_handle by chance
then we would release it without acquiring it first.  Actually I could
initialize it to zero and that would be better, no?

regards,
dan carpenter