linux-kernel - Re: [PATCH v2] Introduce Intel RAPL cooling device driver

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Message-ID: <20130412083203.13cf56b0@chromoly>
Date:	Fri, 12 Apr 2013 08:32:03 -0700
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Joe Perches <joe@...ches.com>, LKML <linux-kernel@...r.kernel.org>,
	Platform Driver <platform-driver-x86@...r.kernel.org>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Paul Bolle <pebolle@...cali.nl>
Subject: Re: [PATCH v2] Introduce Intel RAPL cooling device driver

On Fri, 5 Apr 2013 14:35:18 -0700
Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:

> On Fri, Apr 05, 2013 at 02:26:35PM -0700, Joe Perches wrote:
> > On Fri, 2013-04-05 at 14:02 -0700, Jacob Pan wrote:
> > > +static ssize_t store_event_control(struct device *dev,
> > > +				struct device_attribute *attr,
> > > +				const char *buf,
> > > +				size_t size)
> > > +{
> > > +	struct rapl_domain *rd = dev_get_drvdata(dev);
> > > +	unsigned int efd, new_threshold;
> > > +	struct file *efile = NULL;
> > > +	int ret = 0;
> > > +	int prim;
> > > +	struct rapl_event *ep;
> > > +	u64 val;
> > > +	char cmd[MAX_PRIM_NAME];
> > > +
> > > +	if (sscanf(buf, "%u %s %u", &efd, cmd,
> > > &new_threshold) != 3)
> > > +		return -EINVAL;
> > 
> > This sscanf looks fragile.
> > 
> > buf = "1 some_really_long_name_longer_than_MAX_PRIM_NAME 2"
> > 
> > stack overrun.
> > 
> > Where does buf come from?
> 
> It comes from the sysfs core, which limits it to a PAGE_SIZE.  But
> yes, it does look fragile, and flat out wrong, but I'm not going into
> that just yet, as that whole api should just be deleted for now.
> 
> greg k-h
> 
I am just curious to know besides fixing string length check, is the
problem related to the fact that I have more than
one element for the event_control sysfs node?
i.e. <eventfd> <event_name> <threshold>

If so, the reason being I don't know if there is a standard way
to a transaction via sysfs where I can commit multiple inputs
atomically.

-- 
Thanks,

Jacob
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