linux-kernel - Re: [RESEND][PATCH v2] register_console: prevent adding the same console twice

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Message-ID: <20130802103744.GA6356@kroah.com>
Date:	Fri, 2 Aug 2013 18:37:44 +0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Andreas Bießmann <andreas@...ssmann.de>
Cc:	linux-kernel@...r.kernel.org, Kay Sievers <kay@...y.org>,
	Ben Hutchings <ben@...adent.org.uk>, stable@...r.kernel.org
Subject: Re: [RESEND][PATCH v2] register_console: prevent adding the same
 console twice

On Fri, Aug 02, 2013 at 12:23:34PM +0200, Andreas Bießmann wrote:
> This patch guards the console_drivers list to be corrupted. The
> for_each_console() macro insist on a strictly forward list ended by NULL:
> 
>  con0->next->con1->next->NULL
> 
> Without this patch it may happen easily to destroy this list for example by
> adding 'earlyprintk' twice, especially on embedded devices where the early
> console is often a single static instance.  This will result in the following
> list:
> 
>  con0->next->con0
> 
> This in turn will result in an endless loop in console_unlock() later on by
> printing the first __log_buf line endlessly.
> 
> Signed-off-by: Andreas Bießmann <andreas@...ssmann.de>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Kay Sievers <kay@...y.org>
> Cc: Ben Hutchings <ben@...adent.org.uk>
> Cc: stable@...r.kernel.org

It's a nice "feature", but I fail to see how this is worthy of going
into the stable tree, as it's not fixing a kernel error, only a typo by
a user.

thanks,

greg k-h
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