[PATCH 2/3] livepatch: free klp_patch object without holding klp_mutex
From: Ming Lei
Date: Thu Oct 28 2021 - 08:58:16 EST
kobject_del() is called from kobject_put(), and after the klp_patch
kobject is deleted, any show()/store() are done.
Once the klp_patch object is removed from list and prepared for
releasing, no need to hold the global mutex of klp_mutex, so
move the freeing outside of klp_mutex.
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
kernel/livepatch/core.c | 30 ++++++++++++++++++------------
kernel/livepatch/core.h | 3 +--
kernel/livepatch/transition.c | 23 +++++++++++++++++------
kernel/livepatch/transition.h | 2 +-
4 files changed, 37 insertions(+), 21 deletions(-)
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index b967b4b0071b..9ede093d699a 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -327,7 +327,8 @@ int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
* /sys/kernel/livepatch/<patch>/<object>
* /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
*/
-static int __klp_disable_patch(struct klp_patch *patch);
+static int __klp_disable_patch(struct klp_patch *patch,
+ struct list_head *to_free);
static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t count)
@@ -335,6 +336,7 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
struct klp_patch *patch;
int ret;
bool enabled;
+ LIST_HEAD(to_free);
ret = kstrtobool(buf, &enabled);
if (ret)
@@ -360,13 +362,15 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
if (patch == klp_transition_patch)
klp_reverse_transition();
else if (!enabled)
- ret = __klp_disable_patch(patch);
+ ret = __klp_disable_patch(patch, &to_free);
else
ret = -EINVAL;
out:
mutex_unlock(&klp_mutex);
+ klp_free_patches_async(&to_free);
+
if (ret)
return ret;
return count;
@@ -693,20 +697,19 @@ static void klp_free_patch_work_fn(struct work_struct *work)
klp_free_patch_finish(patch);
}
-void klp_free_patch_async(struct klp_patch *patch)
+static void klp_free_patch_async(struct klp_patch *patch)
{
klp_free_patch_start(patch);
schedule_work(&patch->free_work);
}
-void klp_free_replaced_patches_async(struct klp_patch *new_patch)
+void klp_free_patches_async(struct list_head *to_free)
{
- struct klp_patch *old_patch, *tmp_patch;
+ struct klp_patch *patch, *tmp_patch;
- klp_for_each_patch_safe(old_patch, tmp_patch) {
- if (old_patch == new_patch)
- return;
- klp_free_patch_async(old_patch);
+ list_for_each_entry_safe(patch, tmp_patch, to_free, list) {
+ list_del_init(&patch->list);
+ klp_free_patch_async(patch);
}
}
@@ -915,7 +918,8 @@ static int klp_init_patch(struct klp_patch *patch)
return 0;
}
-static int __klp_disable_patch(struct klp_patch *patch)
+static int __klp_disable_patch(struct klp_patch *patch,
+ struct list_head *to_free)
{
struct klp_object *obj;
@@ -942,7 +946,7 @@ static int __klp_disable_patch(struct klp_patch *patch)
klp_start_transition();
patch->enabled = false;
- klp_try_complete_transition();
+ klp_try_complete_transition(to_free);
return 0;
}
@@ -951,6 +955,7 @@ static int __klp_enable_patch(struct klp_patch *patch)
{
struct klp_object *obj;
int ret;
+ LIST_HEAD(unused);
if (klp_transition_patch)
return -EBUSY;
@@ -992,7 +997,8 @@ static int __klp_enable_patch(struct klp_patch *patch)
klp_start_transition();
patch->enabled = true;
- klp_try_complete_transition();
+ klp_try_complete_transition(&unused);
+ WARN_ON_ONCE(!list_empty(&unused));
return 0;
err:
diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h
index 38209c7361b6..8ff97745ba40 100644
--- a/kernel/livepatch/core.h
+++ b/kernel/livepatch/core.h
@@ -13,8 +13,7 @@ extern struct list_head klp_patches;
#define klp_for_each_patch(patch) \
list_for_each_entry(patch, &klp_patches, list)
-void klp_free_patch_async(struct klp_patch *patch);
-void klp_free_replaced_patches_async(struct klp_patch *new_patch);
+void klp_free_patches_async(struct list_head *to_free);
void klp_unpatch_replaced_patches(struct klp_patch *new_patch);
void klp_discard_nops(struct klp_patch *new_patch);
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 291b857a6e20..a9ebc9c5db02 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -32,12 +32,16 @@ static unsigned int klp_signals_cnt;
*/
static void klp_transition_work_fn(struct work_struct *work)
{
+ LIST_HEAD(to_free);
+
mutex_lock(&klp_mutex);
if (klp_transition_patch)
- klp_try_complete_transition();
+ klp_try_complete_transition(&to_free);
mutex_unlock(&klp_mutex);
+
+ klp_free_patches_async(&to_free);
}
static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn);
@@ -384,7 +388,7 @@ static void klp_send_signals(void)
*
* If any tasks are still stuck in the initial patch state, schedule a retry.
*/
-void klp_try_complete_transition(void)
+void klp_try_complete_transition(struct list_head *to_free)
{
unsigned int cpu;
struct task_struct *g, *task;
@@ -449,10 +453,17 @@ void klp_try_complete_transition(void)
* klp_complete_transition() but it is called also
* from klp_cancel_transition().
*/
- if (!patch->enabled)
- klp_free_patch_async(patch);
- else if (patch->replace)
- klp_free_replaced_patches_async(patch);
+ if (!patch->enabled) {
+ list_move(&patch->list, to_free);
+ } else if (patch->replace) {
+ struct klp_patch *old_patch, *tmp_patch;
+
+ klp_for_each_patch_safe(old_patch, tmp_patch) {
+ if (old_patch == patch)
+ break;
+ list_move(&old_patch->list, to_free);
+ }
+ }
}
/*
diff --git a/kernel/livepatch/transition.h b/kernel/livepatch/transition.h
index 322db16233de..20e3a5a0cbce 100644
--- a/kernel/livepatch/transition.h
+++ b/kernel/livepatch/transition.h
@@ -9,7 +9,7 @@ extern struct klp_patch *klp_transition_patch;
void klp_init_transition(struct klp_patch *patch, int state);
void klp_cancel_transition(void);
void klp_start_transition(void);
-void klp_try_complete_transition(void);
+void klp_try_complete_transition(struct list_head *to_free);
void klp_reverse_transition(void);
void klp_force_transition(void);
--
2.31.1