On Mon 2019-02-11 11:05:17, Joe Lawrence wrote:
> There are scenarios where it may not be safe to disable a livepatch once
> it has been enabled. Add a 'sticky' bool to struct klp_patch so that
> livepatches can indicate this to the core. If set, the livepatch may
> not be directly disabled/unloaded.
I agree that this feature might make the life easier in some
situations.
> diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
> index 70d5354e11a8..a33ce73015ba 100644
> --- a/include/linux/livepatch.h
> +++ b/include/linux/livepatch.h
> @@ -151,6 +151,7 @@ struct klp_object {
> * @mod: reference to the live patch module
> * @objs: object entries for kernel objects to be patched
> * @version: patch version number
> + * @sticky: patch can be replaced, but not disabled
I have to admit that the global version and enforcing
the order is useful here to start simple.
> * @replace: replace all actively used patches
> * @list: list node for global list of actively used patches
> * @kobj: kobject for sysfs resources
> @@ -166,6 +167,7 @@ struct klp_patch {
> struct module *mod;
> struct klp_object *objs;
> unsigned int version;
> + bool sticky;
> bool replace;
>
> /* internal */
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index cc120b5018e1..50bf39ec2a9d 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -380,7 +380,7 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
> */
> if (patch == klp_transition_patch)
> klp_reverse_transition();
> - else if (!enabled)
> + else if (!enabled && !patch->sticky)
> ret = __klp_disable_patch(patch);
Hmm, I could imagine that even the revert would not be safe.
A problematic operations might be done already by pre-patch
callbacks or by already patched threads.
Note that the value might be false by default. It might
be set later by a callback on whatever stage it needs
to be set.
If the transition is safe then the problematic
operation need to be done by a callback anyway.
Best Regards,
Petr
PS: Heh, I think that I am too fast with answering. I need to think
more about it.
