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 <[email protected]>
Cc: Kay Sievers <[email protected]>
Cc: Ben Hutchings <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions