netdev - Re: [net-next:master 122/152] drivers/ptp/ptp_chardev.c:36 ptp_ioctl() warn: 'sysoff' puts 832 bytes on stack

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Date:	Fri, 02 Nov 2012 21:39:28 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	richardcochran@...il.com
Cc:	yuanhan.liu@...ux.intel.com, changlongx.xie@...el.com,
	fengguang.wu@...el.com, netdev@...r.kernel.org
Subject: Re: [net-next:master 122/152] drivers/ptp/ptp_chardev.c:36
 ptp_ioctl() warn: 'sysoff' puts 832 bytes on stack

From: Richard Cochran <richardcochran@...il.com>
Date: Fri, 2 Nov 2012 09:59:15 +0100

> On Fri, Nov 02, 2012 at 10:06:31AM +0800, Yuanhan Liu wrote:
>> 
>> Hi Richard,
>> 
>> _just_ FYI and let you aware of it, there are new smatch warnings show up in
>> 
>> tree:   git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git master
>> head:   b77bc2069d1e437d5a1a71bb5cfcf4556ee40015
>> commit: 215b13dd288c2e1e4461c1530a801f5f83e8cd90 [122/152] ptp: add an ioctl to compare PHC time with system time
>> 
>> + drivers/ptp/ptp_chardev.c:36 ptp_ioctl() warn: 'sysoff' puts 832 bytes on stack
>>   drivers/ptp/ptp_chardev.c:144 ptp_read() warn: 'event' puts 960 bytes on stack
> 
> I am aware that these methods use large stack buffers, but I thought
> it was okay seeing as they are both under the 1k limit.

I think you should avoid such a local stack variable here.

It's not that big of a deal to use kmalloc or whatever so just
do that and add the necessary kfree cleanups et al.
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