register_console: prevent adding the same console twice
authorAndreas Bießmann <andreas@biessmann.de>
Fri, 2 Aug 2013 10:23:34 +0000 (12:23 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 5 Aug 2013 07:06:46 +0000 (15:06 +0800)
commit16cf48a6d3e8f9ebe3c3231c12cbe4b0c4ed4d24
tree89232d017899e647deb2a7ce58a45277c7c2998c
parent3855ae1c486a2d1b65a96fac8d504ef7197e62cd
register_console: prevent adding the same console twice

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@biessmann.de>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/printk/printk.c