On Sat, 12 Mar 2022, Chengming Zhou wrote:
> module_put() is not called for a patch with "forced" flag. It should
> block the removal of the livepatch module when the code might still
> be in use after forced transition.
>
> klp_force_transition() currently sets "forced" flag for all patches on
> the list.
>
> In fact, any patch can be safely unloaded when it passed through
> the consistency model in KLP_UNPATCHED transition.
>
> By other words, the "forced" flag must be set only for livepatches
s/By/In/
> that are being removed. In particular, set the "forced" flag:
>
> + only for klp_transition_patch when the transition to KLP_UNPATCHED
> state was forced.
>
> + all replaced patches when the transition to KLP_PATCHED state was
> forced and the patch was replacing the existing patches.
>
> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> ---
> Changes in v3:
> - rewrite more clear commit message by Petr.
>
> Changes in v2:
> - interact nicely with the atomic replace feature noted by Miroslav.
> ---
> kernel/livepatch/transition.c | 16 ++++++++++++++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
> index 5683ac0d2566..7f25a5ae89f6 100644
> --- a/kernel/livepatch/transition.c
> +++ b/kernel/livepatch/transition.c
> @@ -641,6 +641,18 @@ void klp_force_transition(void)
> for_each_possible_cpu(cpu)
> klp_update_patch_state(idle_task(cpu));
>
> - klp_for_each_patch(patch)
> - patch->forced = true;
> + /*
> + * Only need to set forced flag for the transition patch
> + * when force transition to KLP_UNPATCHED state, but
> + * have to set forced flag for all replaced patches
> + * when force atomic replace transition.
> + */
How about something like
/*
* Set forced flag for patches being removed, which is the transition
* patch in KLP_UNPATCHED state or all replaced patches when forcing
* the atomic replace transition.
*/
?
> + if (klp_target_state == KLP_UNPATCHED)
> + klp_transition_patch->forced = true;
> + else if (klp_transition_patch->replace) {
> + klp_for_each_patch(patch) {
> + if (patch != klp_transition_patch)
> + patch->forced = true;
> + }
> + }
Looks good to me.
Miroslav
