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. 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 <andr...@biessmann.de> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> Cc: Kay Sievers <k...@vrfy.org> Cc: sta...@vger.kernel.org --- kernel/printk.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/printk.c b/kernel/printk.c index 0b31715..f78bfcd 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -2254,6 +2254,14 @@ void register_console(struct console *newcon) unsigned long flags; struct console *bcon = NULL; + if (console_drivers) + for_each_console(bcon) + if (bcon == newcon) { + pr_warn("prevent adding console '%s%d' twice\n", + newcon->name, newcon->index); + return; + } + /* * before we register a new CON_BOOT console, make sure we don't * already have a valid console -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/