linux-kernel - Re: [PATCH] drivers/base: Fix length checks in create_syslog_header()/dev_vprintk

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Date:	Fri, 27 Dec 2013 11:17:05 -0800
From:	Joe Perches <joe@...ches.com>
To:	Ben Hutchings <ben@...adent.org.uk>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Kay Sievers <kay@...y.org>
Subject: Re: [PATCH] drivers/base: Fix length checks in
 create_syslog_header()/dev_vprintk_emit()

On Fri, 2013-12-27 at 20:10 +0100, Ben Hutchings wrote:
> On Fri, 2013-12-27 at 10:47 -0800, Greg Kroah-Hartman wrote:
> > On Fri, Dec 27, 2013 at 06:18:18PM +0100, Ben Hutchings wrote:
> > > snprintf() returns the number of bytes that could have been written
> > > (excluding the null), not the actual number of bytes written.  Given a
> > > long enough subsystem or device name, these functions will advance
> > > beyond the end of the on-stack buffer in dev_vprintk_exit(), resulting
> > > in an information leak or stack corruption.  I don't know whether such
> > > a long name is currently possible.
> > > 
> > > In case snprintf() returns a value >= the buffer size, do not add
> > > structured logging information.  Also WARN the first time this
> > > happens, so we can fix the driver or increase the buffer size.
[]
> > > diff --git a/drivers/base/core.c b/drivers/base/core.c
[]
> > > +overflow:
> > > +	dev_WARN_ONCE(dev, 1, "device/subsystem name too long");
> > 
> > Why only warn once?  Any device/subsystem mix should be complained
> > about, if for only that we should be really annoying about it to get it
> > resolved.
> 
> This would expand the volume of logging for the problem device by a
> factor of ~50 so it doesn't seem like a good failure mode.

There are at least 6 bits on struct device unused.
Maybe add another bool bit field to struct device?

	bool			offline_disabled:1;
	bool			offline:1;


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