| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20211102145932.3623108-4-ming.lei@redhat.com>
Date: Tue, 2 Nov 2021 22:59:32 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Josh Poimboeuf <jpoimboe@...hat.com>,
Jiri Kosina <jikos@...nel.org>,
Miroslav Benes <mbenes@...e.cz>,
Petr Mladek <pmladek@...e.com>, live-patching@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Luis Chamberlain <mcgrof@...nel.org>,
Joe Lawrence <joe.lawrence@...hat.com>,
Ming Lei <ming.lei@...hat.com>
Subject: [PATCH V4 3/3] livepatch: free klp_patch object synchronously
klp_mutex isn't acquired before calling kobject_put(klp_patch), so it is
fine to free klp_patch object synchronously.
One issue is that enabled store() method, in which the klp_patch kobject
itself is deleted & released. However, sysfs has provided APIs for dealing
with this corner case, so use sysfs_break_active_protection() and
sysfs_unbreak_active_protection() for releasing klp_patch kobject from
enabled_store(), meantime the enabled attribute has to be removed
before deleting the klp_patch kobject.
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
include/linux/livepatch.h | 1 -
kernel/livepatch/core.c | 37 +++++++++++++++--------------------
kernel/livepatch/core.h | 2 +-
kernel/livepatch/transition.c | 2 +-
4 files changed, 18 insertions(+), 24 deletions(-)
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 9712818997c5..4dcebf52fac5 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -169,7 +169,6 @@ struct klp_patch {
struct list_head obj_list;
bool enabled;
bool forced;
- struct work_struct free_work;
};
#define klp_for_each_object_static(patch, obj) \
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 27768bb5a38c..36999cddc011 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -337,6 +337,7 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
int ret;
bool enabled;
LIST_HEAD(to_free);
+ struct kernfs_node *kn = NULL;
ret = kstrtobool(buf, &enabled);
if (ret)
@@ -369,10 +370,18 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
out:
mutex_unlock(&klp_mutex);
- klp_free_patches_async(&to_free);
-
if (ret)
return ret;
+
+ if (!list_empty(&to_free)) {
+ kn = sysfs_break_active_protection(kobj, &attr->attr);
+ WARN_ON_ONCE(!kn);
+ sysfs_remove_file(kobj, &attr->attr);
+ klp_free_patches(&to_free);
+ if (kn)
+ sysfs_unbreak_active_protection(kn);
+ }
+
return count;
}
@@ -684,32 +693,19 @@ static void klp_free_patch_finish(struct klp_patch *patch)
kobject_put(&patch->kobj);
}
-/*
- * The livepatch might be freed from sysfs interface created by the patch.
- * This work allows to wait until the interface is destroyed in a separate
- * context.
- */
-static void klp_free_patch_work_fn(struct work_struct *work)
-{
- struct klp_patch *patch =
- container_of(work, struct klp_patch, free_work);
-
- klp_free_patch_finish(patch);
-}
-
-static void klp_free_patch_async(struct klp_patch *patch)
+static void klp_free_patch(struct klp_patch *patch)
{
klp_free_patch_start(patch);
- schedule_work(&patch->free_work);
+ klp_free_patch_finish(patch);
}
-void klp_free_patches_async(struct list_head *to_free)
+void klp_free_patches(struct list_head *to_free)
{
struct klp_patch *patch, *tmp_patch;
list_for_each_entry_safe(patch, tmp_patch, to_free, list) {
list_del_init(&patch->list);
- klp_free_patch_async(patch);
+ klp_free_patch(patch);
}
}
@@ -873,7 +869,6 @@ static int klp_init_patch_early(struct klp_patch *patch)
kobject_init(&patch->kobj, &klp_ktype_patch);
patch->enabled = false;
patch->forced = false;
- INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
klp_for_each_object_static(patch, obj) {
if (!obj->funcs)
@@ -1067,7 +1062,7 @@ int klp_enable_patch(struct klp_patch *patch)
mutex_unlock(&klp_mutex);
- klp_free_patches_async(&to_free);
+ klp_free_patches(&to_free);
return 0;
diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h
index 8ff97745ba40..ea593f370049 100644
--- a/kernel/livepatch/core.h
+++ b/kernel/livepatch/core.h
@@ -13,7 +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_patches_async(struct list_head *to_free);
+void klp_free_patches(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 0c1857405c17..1a339a076dd4 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -40,7 +40,7 @@ static void klp_transition_work_fn(struct work_struct *work)
mutex_unlock(&klp_mutex);
- klp_free_patches_async(&to_free);
+ klp_free_patches(&to_free);
}
static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn);
--
2.31.1
Powered by blists - more mailing lists