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SubjectRe: [PATCH] livepatch: Enhance livepatch to support remove patch module dynamically
On Wed, 1 Apr 2015, Minfei Huang wrote:

> As mentioned in the annotation, the patch module would not permit to
> be removed once it is loaded.
>
> Kernel may crash in the case that the function in the patch module is
> called during removing.
>
> We will increase the module reference when the patch module is enable,
> so that the module cannt be removed. Once the module is disable, it will
> be removed.
>
> Signed-off-by: Minfei Huang <minfei.huang@yahoo.com>
> ---
> kernel/livepatch/core.c | 47 +++++++++++++++++++++++++++++++----------------
> 1 file changed, 31 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 3f9f1d6..0266950 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -502,6 +502,17 @@ static int __klp_disable_patch(struct klp_patch *patch)
> return 0;
> }
>
> +static int __klp_disable_patch_nolock(struct klp_patch *patch)
> +{
> + int ret = 0;
> +
> + ret = __klp_disable_patch(patch);
> + if (ret)
> + return ret;
> + module_put(patch->mod);
> + return ret;
> +}
> +

Your patch doesn't solve the problem at all.

There is no guarantee that once __klp_disable_patch() returns noone is
using the old code any more.

--
Jiri Kosina
SUSE Labs


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