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authorPetr Mladek <pmladek@suse.com>2019-01-09 13:43:22 +0100
committerJiri Kosina <jkosina@suse.cz>2019-01-11 20:51:24 +0100
commit68007289bf3cd937a5b8fc4987d2787167bd06ca (patch)
tree2c913929da4c5e65fcacdfc5afb47399d86cf446
parent0430f78bf38f9972f0cf0522709cc63d49fa164c (diff)
livepatch: Don't block the removal of patches loaded after a forced transition
module_put() is currently never called in klp_complete_transition() when klp_force is set. As a result, we might keep the reference count even when klp_enable_patch() fails and klp_cancel_transition() is called. This might give the impression that a module might get blocked in some strange init state. Fortunately, it is not the case. The reference count is ignored when mod->init fails and erroneous modules are always removed. Anyway, this might be confusing. Instead, this patch moves the global klp_forced flag into struct klp_patch. As a result, we block only modules that might still be in use after a forced transition. Newly loaded livepatches might be eventually completely removed later. It is not a big deal. But the code is at least consistent with the reality. Signed-off-by: Petr Mladek <pmladek@suse.com> Acked-by: Joe Lawrence <joe.lawrence@redhat.com> Acked-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
-rw-r--r--include/linux/livepatch.h2
-rw-r--r--kernel/livepatch/core.c4
-rw-r--r--kernel/livepatch/core.h1
-rw-r--r--kernel/livepatch/transition.c10
4 files changed, 11 insertions, 6 deletions
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 6978785bc059..6a9165d9b090 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -143,6 +143,7 @@ struct klp_object {
* @kobj: kobject for sysfs resources
* @kobj_added: @kobj has been added and needs freeing
* @enabled: the patch is enabled (but operation may be incomplete)
+ * @forced: was involved in a forced transition
* @finish: for waiting till it is safe to remove the patch module
*/
struct klp_patch {
@@ -155,6 +156,7 @@ struct klp_patch {
struct kobject kobj;
bool kobj_added;
bool enabled;
+ bool forced;
struct completion finish;
};
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 6f0d9095f662..e77c5017ae0c 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -45,7 +45,8 @@
*/
DEFINE_MUTEX(klp_mutex);
-static LIST_HEAD(klp_patches);
+/* Registered patches */
+LIST_HEAD(klp_patches);
static struct kobject *klp_root_kobj;
@@ -659,6 +660,7 @@ static int klp_init_patch_early(struct klp_patch *patch)
INIT_LIST_HEAD(&patch->list);
patch->kobj_added = false;
patch->enabled = false;
+ patch->forced = false;
init_completion(&patch->finish);
klp_for_each_object(patch, obj) {
diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h
index 48a83d4364cf..d0cb5390e247 100644
--- a/kernel/livepatch/core.h
+++ b/kernel/livepatch/core.h
@@ -5,6 +5,7 @@
#include <linux/livepatch.h>
extern struct mutex klp_mutex;
+extern struct list_head klp_patches;
static inline bool klp_is_object_loaded(struct klp_object *obj)
{
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index f27a378ad5e1..a4c921364003 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -33,8 +33,6 @@ struct klp_patch *klp_transition_patch;
static int klp_target_state = KLP_UNDEFINED;
-static bool klp_forced = false;
-
/*
* This work can be performed periodically to finish patching or unpatching any
* "straggler" tasks which failed to transition in the first attempt.
@@ -137,10 +135,10 @@ static void klp_complete_transition(void)
klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
/*
- * klp_forced set implies unbounded increase of module's ref count if
+ * patch->forced set implies unbounded increase of module's ref count if
* the module is disabled/enabled in a loop.
*/
- if (!klp_forced && klp_target_state == KLP_UNPATCHED)
+ if (!klp_transition_patch->forced && klp_target_state == KLP_UNPATCHED)
module_put(klp_transition_patch->mod);
klp_target_state = KLP_UNDEFINED;
@@ -620,6 +618,7 @@ void klp_send_signals(void)
*/
void klp_force_transition(void)
{
+ struct klp_patch *patch;
struct task_struct *g, *task;
unsigned int cpu;
@@ -633,5 +632,6 @@ void klp_force_transition(void)
for_each_possible_cpu(cpu)
klp_update_patch_state(idle_task(cpu));
- klp_forced = true;
+ list_for_each_entry(patch, &klp_patches, list)
+ patch->forced = true;
}