From: Andreas Bießmann Date: Fri, 2 Aug 2013 10:23:34 +0000 (+0200) Subject: register_console: prevent adding the same console twice X-Git-Tag: firefly_0821_release~176^2~5470^2~81 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=16cf48a6d3e8f9ebe3c3231c12cbe4b0c4ed4d24;p=firefly-linux-kernel-4.4.55.git 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 Cc: Kay Sievers Cc: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 5b5a7080e2a5..b4e8500afdb3 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -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