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From: Dan Carpenter <dan.carpenter@oracle.com>
To: "Gabriel L. Somlo" <somlo@cmu.edu>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	qemu-devel@nongnu.org, linux-kernel@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: Re: [patch] firmware: qemu_fw_cfg.c: potential unintialized variable
Date: Thu, 14 Apr 2016 19:12:53 +0000	[thread overview]
Message-ID: <20160414191253.GH4247@mwanda> (raw)
In-Reply-To: <20160414184005.GC7821@HEDWIG.INI.CMU.EDU>

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


WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <dan.carpenter@oracle.com>
To: "Gabriel L. Somlo" <somlo@cmu.edu>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	qemu-devel@nongnu.org, linux-kernel@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: Re: [patch] firmware: qemu_fw_cfg.c: potential unintialized variable
Date: Thu, 14 Apr 2016 22:12:53 +0300	[thread overview]
Message-ID: <20160414191253.GH4247@mwanda> (raw)
In-Reply-To: <20160414184005.GC7821@HEDWIG.INI.CMU.EDU>

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

WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <dan.carpenter@oracle.com>
To: "Gabriel L. Somlo" <somlo@cmu.edu>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	qemu-devel@nongnu.org, linux-kernel@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: Re: [Qemu-devel] [patch] firmware: qemu_fw_cfg.c: potential unintialized variable
Date: Thu, 14 Apr 2016 22:12:53 +0300	[thread overview]
Message-ID: <20160414191253.GH4247@mwanda> (raw)
In-Reply-To: <20160414184005.GC7821@HEDWIG.INI.CMU.EDU>

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

  reply	other threads:[~2016-04-14 19:12 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-14  9:33 [patch] firmware: qemu_fw_cfg.c: potential unintialized variable Dan Carpenter
2016-04-14  9:33 ` [Qemu-devel] " Dan Carpenter
2016-04-14  9:33 ` Dan Carpenter
2016-04-14 18:40 ` Gabriel L. Somlo
2016-04-14 18:40   ` [Qemu-devel] " Gabriel L. Somlo
2016-04-14 18:40   ` Gabriel L. Somlo
2016-04-14 19:12   ` Dan Carpenter [this message]
2016-04-14 19:12     ` [Qemu-devel] " Dan Carpenter
2016-04-14 19:12     ` Dan Carpenter
2016-04-14 19:36     ` Gabriel L. Somlo
2016-04-14 19:36       ` [Qemu-devel] " Gabriel L. Somlo
2016-04-14 19:36       ` Gabriel L. Somlo
2016-04-14 20:05       ` Dan Carpenter
2016-04-14 20:05         ` [Qemu-devel] " Dan Carpenter
2016-04-14 20:05         ` Dan Carpenter
2016-04-14 19:51 ` Gabriel L. Somlo
2016-04-14 19:51   ` [Qemu-devel] " Gabriel L. Somlo
2016-04-14 19:51   ` Gabriel L. Somlo

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