linux-kernel - Re: [PATCH v2] livepatch: unpatch all klp_objects if klp_module

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Date:   Thu, 5 Oct 2017 16:55:43 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Joe Lawrence <joe.lawrence@...hat.com>
Cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jessica Yu <jeyu@...nel.org>, Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>, Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH v2] livepatch: unpatch all klp_objects if
 klp_module_coming fails

On Mon, Oct 02, 2017 at 11:56:48AM -0400, Joe Lawrence wrote:
> When an incoming module is considered for livepatching by
> klp_module_coming(), it iterates over multiple patches and multiple
> kernel objects in this order:
> 
> 	list_for_each_entry(patch, &klp_patches, list) {
> 		klp_for_each_object(patch, obj) {
> 
> which means that if one of the kernel objects fails to patch,
> klp_module_coming()'s error path needs to unpatch and cleanup any kernel
> objects that were already patched by a previous patch.
> 
> Reported-by: Miroslav Benes <mbenes@...e.cz>
> Suggested-by: Petr Mladek <pmladek@...e.com>
> Signed-off-by: Joe Lawrence <joe.lawrence@...hat.com>
> ---
> v2:
> 
>  - cleanup comment describing the new function
>  - s/klp_cleanup_module_objects_limited/klp_cleanup_module_patches_limited
>  - added a suggested-by tag for Petr since he suggested both code and
>    commentary :)
> 
>  kernel/livepatch/core.c | 60 ++++++++++++++++++++++++++++++-------------------
>  1 file changed, 37 insertions(+), 23 deletions(-)
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index b9628e43c78f..bf8c8fd72589 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -830,6 +830,41 @@ int klp_register_patch(struct klp_patch *patch)
>  }
>  EXPORT_SYMBOL_GPL(klp_register_patch);
>  
> +/*
> + * Remove parts of patches that touch a given kernel module. The list of
> + * patches processed might be limited. When limit is NULL, all patches
> + * will be handled.
> + */
> +static void klp_cleanup_module_patches_limited(struct module *mod,
> +					       struct klp_patch *limit)

One nit, I think the function name is too verbose.  It already has a
'limit' argument, so I think putting 'limited' in the name is too much
detail.  I would just call it klp_cleanup_module_patches().

Otherwise the patch looks great.  Thanks for fixing it!

Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>

-- 
Josh