Re: [PATCH 2/2] kernel: add support for live patching

[Andy Lutomirski]

On 11/06/2014 06:39 AM, Seth Jennings wrote:
> This commit introduces code for the live patching core.  It implements
> an ftrace-based mechanism and kernel interface for doing live patching
> of kernel and kernel module functions.
> 
> It represents the greatest common functionality set between kpatch and
> kgraft and can accept patches built using either method.
> 
> This first version does not implement any consistency mechanism that
> ensures that old and new code do not run together.  In practice, ~90% of
> CVEs are safe to apply in this way, since they simply add a conditional
> check.  However, any function change that can not execute safely with
> the old version of the function can _not_ be safely applied in this
> version.
> 

[...]

> +/********************************************
> + * Sysfs Interface
> + *******************************************/
> +/*
> + * /sys/kernel/livepatch
> + * /sys/kernel/livepatch/<patch>
> + * /sys/kernel/livepatch/<patch>/enabled
> + * /sys/kernel/livepatch/<patch>/<object>
> + * /sys/kernel/livepatch/<patch>/<object>/<func>
> + * /sys/kernel/livepatch/<patch>/<object>/<func>/new_addr
> + * /sys/kernel/livepatch/<patch>/<object>/<func>/old_addr
> + */

Letting anyone read new_addr and old_addr is a kASLR leak, and I would
argue that showing this information to non-root at all is probably a bad
idea.

Can you make new_addr and old_addr have mode 0600 and
/sys/kernel/livepatch itself have mode 0500?  For the latter, an admin
who wants unprivileged users to be able to see it can easily chmod it.

--Andy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/