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>
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 5b5a708..b4e8500 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2226,6 +2226,13 @@
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