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register_console: prevent adding the same console twice

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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>
This commit is contained in:
Andreas Bießmann 2013-08-02 12:23:34 +02:00 committed by Greg Kroah-Hartman
parent 3855ae1c48
commit 16cf48a6d3
1 changed files with 7 additions and 0 deletions
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7
kernel/printk/printk.c
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@ -2226,6 +2226,13 @@ void register_console(struct console *newcon)
struct console *bcon = NULL;
struct console_cmdline *c;
if (console_drivers)
for_each_console(bcon)
if (WARN(bcon == newcon,
"console '%s%d' already registered\n",
bcon->name, bcon->index))
return;
/*
* before we register a new CON_BOOT console, make sure we don't
* already have a valid console