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

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Message-ID: <1402280170.9150.1.camel@joe-AO725>
Date:	Sun, 08 Jun 2014 19:16:10 -0700
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 v2] drivers/base: Fix length checks in
 create_syslog_header()/dev_vprintk_emit()

On Sun, 2014-06-08 at 23:51 +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.

I believe this is guaranteed to be < 128, but
I also suppose it'd be better to emit whatever
buffer is < 128 and add a WARN_ON_ONCE instead.


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