From: Chengming Zhou <zhouchengming@bytedance.com>
Date: Sat, 12 Mar 2022 23:22:20 +0800
Subject: livepatch: Don't block removal of patches that are safe to unload
Git-commit: 2957308343fa7c621df9f342fab88cb970b8d5f3
Patch-mainline: v5.18-rc1
References: bsc#1071995
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.
In other words, the "forced" flag must be set only for livepatches
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@bytedance.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
[mbenes@suse.cz: wording improvements]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220312152220.88127-1-zhouchengming@bytedance.com
Acked-by: Miroslav Benes <mbenes@suse.cz>
---
kernel/livepatch/transition.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 5683ac0d2566..77ef45a1e0a3 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -641,6 +641,13 @@ 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;
+ /* Set forced flag for patches being removed. */
+ 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;
+ }
+ }
}