linux-kernel - Re: [PATCH v2] drivers/base: Fix length checks in create_syslog_header()/dev_vprintk

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Date:	Fri, 11 Jul 2014 18:20:58 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Joe Perches <joe@...ches.com>,
	Kay Sievers <kay@...y.org>
Subject: Re: [PATCH v2] drivers/base: Fix length checks in
 create_syslog_header()/dev_vprintk_emit()

On Wed, 2014-07-09 at 16:57 -0700, Greg Kroah-Hartman wrote:
> On Sun, Jun 08, 2014 at 11:51:43PM +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 if this happens, so we can
> > fix the driver or increase the buffer size.
> > 
> > Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> > ---
> > v2: use dev_WARN() not dev_WARN_ON()
> 
> This patch breaks the build in a huge way:
> 
> drivers/base/core.c: In function ‘create_syslog_header’:
> drivers/base/core.c:2049:16: error: expected ‘)’ before numeric constant
>   dev_WARN(dev, 1, "device/subsystem name too long");
>                   ^
> 
> is the start of it, it goes on for a page or so after that :(

Sorry about that, I must not have committed the working version before
mailing it.  If you delete the '1, ' it should work.  If you've already
deleted the patch, I'll check and send the working version.

Ben.

-- 
Ben Hutchings
To err is human; to really foul things up requires a computer.

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