On Fri, 2013-03-22 at 11:10 +0100, Andreas Bießmann wrote:
> 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 <andreas@xxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Kay Sievers <kay@xxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> 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);
Since this is surely a bug in the calling driver, I think the warning
should be louder, i.e. use WARN.
Ben.
> + return;
> + }
> +
> /*
> * before we register a new CON_BOOT console, make sure we don't
> * already have a valid console
--
Ben Hutchings
Make three consecutive correct guesses and you will be considered an expert.
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