summaryrefslogtreecommitdiff
path: root/kernel
diff options
context:
space:
mode:
Diffstat (limited to 'kernel')
-rw-r--r--kernel/livepatch/core.c854
-rw-r--r--kernel/livepatch/core.h11
-rw-r--r--kernel/livepatch/patch.c57
-rw-r--r--kernel/livepatch/patch.h5
-rw-r--r--kernel/livepatch/transition.c124
-rw-r--r--kernel/livepatch/transition.h1
6 files changed, 643 insertions, 409 deletions
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 5b77a7314e01..eb0ee10a1981 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -45,7 +45,12 @@
*/
DEFINE_MUTEX(klp_mutex);
-static LIST_HEAD(klp_patches);
+/*
+ * Actively used patches: enabled or in transition. Note that replaced
+ * or disabled patches are not listed even though the related kernel
+ * module still can be loaded.
+ */
+LIST_HEAD(klp_patches);
static struct kobject *klp_root_kobj;
@@ -82,20 +87,43 @@ static void klp_find_object_module(struct klp_object *obj)
mutex_unlock(&module_mutex);
}
-static bool klp_is_patch_registered(struct klp_patch *patch)
+static bool klp_initialized(void)
+{
+ return !!klp_root_kobj;
+}
+
+static struct klp_func *klp_find_func(struct klp_object *obj,
+ struct klp_func *old_func)
{
- struct klp_patch *mypatch;
+ struct klp_func *func;
- list_for_each_entry(mypatch, &klp_patches, list)
- if (mypatch == patch)
- return true;
+ klp_for_each_func(obj, func) {
+ if ((strcmp(old_func->old_name, func->old_name) == 0) &&
+ (old_func->old_sympos == func->old_sympos)) {
+ return func;
+ }
+ }
- return false;
+ return NULL;
}
-static bool klp_initialized(void)
+static struct klp_object *klp_find_object(struct klp_patch *patch,
+ struct klp_object *old_obj)
{
- return !!klp_root_kobj;
+ struct klp_object *obj;
+
+ klp_for_each_object(patch, obj) {
+ if (klp_is_module(old_obj)) {
+ if (klp_is_module(obj) &&
+ strcmp(old_obj->name, obj->name) == 0) {
+ return obj;
+ }
+ } else if (!klp_is_module(obj)) {
+ return obj;
+ }
+ }
+
+ return NULL;
}
struct klp_find_arg {
@@ -278,170 +306,6 @@ static int klp_write_object_relocations(struct module *pmod,
return ret;
}
-static int __klp_disable_patch(struct klp_patch *patch)
-{
- struct klp_object *obj;
-
- if (WARN_ON(!patch->enabled))
- return -EINVAL;
-
- if (klp_transition_patch)
- return -EBUSY;
-
- /* enforce stacking: only the last enabled patch can be disabled */
- if (!list_is_last(&patch->list, &klp_patches) &&
- list_next_entry(patch, list)->enabled)
- return -EBUSY;
-
- klp_init_transition(patch, KLP_UNPATCHED);
-
- klp_for_each_object(patch, obj)
- if (obj->patched)
- klp_pre_unpatch_callback(obj);
-
- /*
- * Enforce the order of the func->transition writes in
- * klp_init_transition() and the TIF_PATCH_PENDING writes in
- * klp_start_transition(). In the rare case where klp_ftrace_handler()
- * is called shortly after klp_update_patch_state() switches the task,
- * this ensures the handler sees that func->transition is set.
- */
- smp_wmb();
-
- klp_start_transition();
- klp_try_complete_transition();
- patch->enabled = false;
-
- return 0;
-}
-
-/**
- * klp_disable_patch() - disables a registered patch
- * @patch: The registered, enabled patch to be disabled
- *
- * Unregisters the patched functions from ftrace.
- *
- * Return: 0 on success, otherwise error
- */
-int klp_disable_patch(struct klp_patch *patch)
-{
- int ret;
-
- mutex_lock(&klp_mutex);
-
- if (!klp_is_patch_registered(patch)) {
- ret = -EINVAL;
- goto err;
- }
-
- if (!patch->enabled) {
- ret = -EINVAL;
- goto err;
- }
-
- ret = __klp_disable_patch(patch);
-
-err:
- mutex_unlock(&klp_mutex);
- return ret;
-}
-EXPORT_SYMBOL_GPL(klp_disable_patch);
-
-static int __klp_enable_patch(struct klp_patch *patch)
-{
- struct klp_object *obj;
- int ret;
-
- if (klp_transition_patch)
- return -EBUSY;
-
- if (WARN_ON(patch->enabled))
- return -EINVAL;
-
- /* enforce stacking: only the first disabled patch can be enabled */
- if (patch->list.prev != &klp_patches &&
- !list_prev_entry(patch, list)->enabled)
- return -EBUSY;
-
- /*
- * A reference is taken on the patch module to prevent it from being
- * unloaded.
- */
- if (!try_module_get(patch->mod))
- return -ENODEV;
-
- pr_notice("enabling patch '%s'\n", patch->mod->name);
-
- klp_init_transition(patch, KLP_PATCHED);
-
- /*
- * Enforce the order of the func->transition writes in
- * klp_init_transition() and the ops->func_stack writes in
- * klp_patch_object(), so that klp_ftrace_handler() will see the
- * func->transition updates before the handler is registered and the
- * new funcs become visible to the handler.
- */
- smp_wmb();
-
- klp_for_each_object(patch, obj) {
- if (!klp_is_object_loaded(obj))
- continue;
-
- ret = klp_pre_patch_callback(obj);
- if (ret) {
- pr_warn("pre-patch callback failed for object '%s'\n",
- klp_is_module(obj) ? obj->name : "vmlinux");
- goto err;
- }
-
- ret = klp_patch_object(obj);
- if (ret) {
- pr_warn("failed to patch object '%s'\n",
- klp_is_module(obj) ? obj->name : "vmlinux");
- goto err;
- }
- }
-
- klp_start_transition();
- klp_try_complete_transition();
- patch->enabled = true;
-
- return 0;
-err:
- pr_warn("failed to enable patch '%s'\n", patch->mod->name);
-
- klp_cancel_transition();
- return ret;
-}
-
-/**
- * klp_enable_patch() - enables a registered patch
- * @patch: The registered, disabled patch to be enabled
- *
- * Performs the needed symbol lookups and code relocations,
- * then registers the patched functions with ftrace.
- *
- * Return: 0 on success, otherwise error
- */
-int klp_enable_patch(struct klp_patch *patch)
-{
- int ret;
-
- mutex_lock(&klp_mutex);
-
- if (!klp_is_patch_registered(patch)) {
- ret = -EINVAL;
- goto err;
- }
-
- ret = __klp_enable_patch(patch);
-
-err:
- mutex_unlock(&klp_mutex);
- return ret;
-}
-EXPORT_SYMBOL_GPL(klp_enable_patch);
-
/*
* Sysfs Interface
*
@@ -449,11 +313,11 @@ EXPORT_SYMBOL_GPL(klp_enable_patch);
* /sys/kernel/livepatch/<patch>
* /sys/kernel/livepatch/<patch>/enabled
* /sys/kernel/livepatch/<patch>/transition
- * /sys/kernel/livepatch/<patch>/signal
* /sys/kernel/livepatch/<patch>/force
* /sys/kernel/livepatch/<patch>/<object>
* /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
*/
+static int __klp_disable_patch(struct klp_patch *patch);
static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t count)
@@ -470,40 +334,32 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
mutex_lock(&klp_mutex);
- if (!klp_is_patch_registered(patch)) {
- /*
- * Module with the patch could either disappear meanwhile or is
- * not properly initialized yet.
- */
- ret = -EINVAL;
- goto err;
- }
-
if (patch->enabled == enabled) {
/* already in requested state */
ret = -EINVAL;
- goto err;
+ goto out;
}
- if (patch == klp_transition_patch) {
+ /*
+ * Allow to reverse a pending transition in both ways. It might be
+ * necessary to complete the transition without forcing and breaking
+ * the system integrity.
+ *
+ * Do not allow to re-enable a disabled patch.
+ */
+ if (patch == klp_transition_patch)
klp_reverse_transition();
- } else if (enabled) {
- ret = __klp_enable_patch(patch);
- if (ret)
- goto err;
- } else {
+ else if (!enabled)
ret = __klp_disable_patch(patch);
- if (ret)
- goto err;
- }
+ else
+ ret = -EINVAL;
+out:
mutex_unlock(&klp_mutex);
+ if (ret)
+ return ret;
return count;
-
-err:
- mutex_unlock(&klp_mutex);
- return ret;
}
static ssize_t enabled_show(struct kobject *kobj,
@@ -525,35 +381,6 @@ static ssize_t transition_show(struct kobject *kobj,
patch == klp_transition_patch);
}
-static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
- const char *buf, size_t count)
-{
- struct klp_patch *patch;
- int ret;
- bool val;
-
- ret = kstrtobool(buf, &val);
- if (ret)
- return ret;
-
- if (!val)
- return count;
-
- mutex_lock(&klp_mutex);
-
- patch = container_of(kobj, struct klp_patch, kobj);
- if (patch != klp_transition_patch) {
- mutex_unlock(&klp_mutex);
- return -EINVAL;
- }
-
- klp_send_signals();
-
- mutex_unlock(&klp_mutex);
-
- return count;
-}
-
static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t count)
{
@@ -585,16 +412,129 @@ static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
-static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);
static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
static struct attribute *klp_patch_attrs[] = {
&enabled_kobj_attr.attr,
&transition_kobj_attr.attr,
- &signal_kobj_attr.attr,
&force_kobj_attr.attr,
NULL
};
+static void klp_free_object_dynamic(struct klp_object *obj)
+{
+ kfree(obj->name);
+ kfree(obj);
+}
+
+static struct klp_object *klp_alloc_object_dynamic(const char *name)
+{
+ struct klp_object *obj;
+
+ obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+ if (!obj)
+ return NULL;
+
+ if (name) {
+ obj->name = kstrdup(name, GFP_KERNEL);
+ if (!obj->name) {
+ kfree(obj);
+ return NULL;
+ }
+ }
+
+ INIT_LIST_HEAD(&obj->func_list);
+ obj->dynamic = true;
+
+ return obj;
+}
+
+static void klp_free_func_nop(struct klp_func *func)
+{
+ kfree(func->old_name);
+ kfree(func);
+}
+
+static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
+ struct klp_object *obj)
+{
+ struct klp_func *func;
+
+ func = kzalloc(sizeof(*func), GFP_KERNEL);
+ if (!func)
+ return NULL;
+
+ if (old_func->old_name) {
+ func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
+ if (!func->old_name) {
+ kfree(func);
+ return NULL;
+ }
+ }
+
+ /*
+ * func->new_func is same as func->old_func. These addresses are
+ * set when the object is loaded, see klp_init_object_loaded().
+ */
+ func->old_sympos = old_func->old_sympos;
+ func->nop = true;
+
+ return func;
+}
+
+static int klp_add_object_nops(struct klp_patch *patch,
+ struct klp_object *old_obj)
+{
+ struct klp_object *obj;
+ struct klp_func *func, *old_func;
+
+ obj = klp_find_object(patch, old_obj);
+
+ if (!obj) {
+ obj = klp_alloc_object_dynamic(old_obj->name);
+ if (!obj)
+ return -ENOMEM;
+
+ list_add_tail(&obj->node, &patch->obj_list);
+ }
+
+ klp_for_each_func(old_obj, old_func) {
+ func = klp_find_func(obj, old_func);
+ if (func)
+ continue;
+
+ func = klp_alloc_func_nop(old_func, obj);
+ if (!func)
+ return -ENOMEM;
+
+ list_add_tail(&func->node, &obj->func_list);
+ }
+
+ return 0;
+}
+
+/*
+ * Add 'nop' functions which simply return to the caller to run
+ * the original function. The 'nop' functions are added to a
+ * patch to facilitate a 'replace' mode.
+ */
+static int klp_add_nops(struct klp_patch *patch)
+{
+ struct klp_patch *old_patch;
+ struct klp_object *old_obj;
+
+ klp_for_each_patch(old_patch) {
+ klp_for_each_object(old_patch, old_obj) {
+ int err;
+
+ err = klp_add_object_nops(patch, old_obj);
+ if (err)
+ return err;
+ }
+ }
+
+ return 0;
+}
+
static void klp_kobj_release_patch(struct kobject *kobj)
{
struct klp_patch *patch;
@@ -611,6 +551,12 @@ static struct kobj_type klp_ktype_patch = {
static void klp_kobj_release_object(struct kobject *kobj)
{
+ struct klp_object *obj;
+
+ obj = container_of(kobj, struct klp_object, kobj);
+
+ if (obj->dynamic)
+ klp_free_object_dynamic(obj);
}
static struct kobj_type klp_ktype_object = {
@@ -620,6 +566,12 @@ static struct kobj_type klp_ktype_object = {
static void klp_kobj_release_func(struct kobject *kobj)
{
+ struct klp_func *func;
+
+ func = container_of(kobj, struct klp_func, kobj);
+
+ if (func->nop)
+ klp_free_func_nop(func);
}
static struct kobj_type klp_ktype_func = {
@@ -627,17 +579,23 @@ static struct kobj_type klp_ktype_func = {
.sysfs_ops = &kobj_sysfs_ops,
};
-/*
- * Free all functions' kobjects in the array up to some limit. When limit is
- * NULL, all kobjects are freed.
- */
-static void klp_free_funcs_limited(struct klp_object *obj,
- struct klp_func *limit)
+static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
{
- struct klp_func *func;
+ struct klp_func *func, *tmp_func;
+
+ klp_for_each_func_safe(obj, func, tmp_func) {
+ if (nops_only && !func->nop)
+ continue;
+
+ list_del(&func->node);
- for (func = obj->funcs; func->old_name && func != limit; func++)
- kobject_put(&func->kobj);
+ /* Might be called from klp_init_patch() error path. */
+ if (func->kobj_added) {
+ kobject_put(&func->kobj);
+ } else if (func->nop) {
+ klp_free_func_nop(func);
+ }
+ }
}
/* Clean up when a patched object is unloaded */
@@ -647,35 +605,111 @@ static void klp_free_object_loaded(struct klp_object *obj)
obj->mod = NULL;
- klp_for_each_func(obj, func)
- func->old_addr = 0;
+ klp_for_each_func(obj, func) {
+ func->old_func = NULL;
+
+ if (func->nop)
+ func->new_func = NULL;
+ }
}
-/*
- * Free all objects' kobjects in the array up to some limit. When limit is
- * NULL, all kobjects are freed.
- */
-static void klp_free_objects_limited(struct klp_patch *patch,
- struct klp_object *limit)
+static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
{
- struct klp_object *obj;
+ struct klp_object *obj, *tmp_obj;
+
+ klp_for_each_object_safe(patch, obj, tmp_obj) {
+ __klp_free_funcs(obj, nops_only);
+
+ if (nops_only && !obj->dynamic)
+ continue;
+
+ list_del(&obj->node);
- for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
- klp_free_funcs_limited(obj, NULL);
- kobject_put(&obj->kobj);
+ /* Might be called from klp_init_patch() error path. */
+ if (obj->kobj_added) {
+ kobject_put(&obj->kobj);
+ } else if (obj->dynamic) {
+ klp_free_object_dynamic(obj);
+ }
}
}
-static void klp_free_patch(struct klp_patch *patch)
+static void klp_free_objects(struct klp_patch *patch)
+{
+ __klp_free_objects(patch, false);
+}
+
+static void klp_free_objects_dynamic(struct klp_patch *patch)
+{
+ __klp_free_objects(patch, true);
+}
+
+/*
+ * This function implements the free operations that can be called safely
+ * under klp_mutex.
+ *
+ * The operation must be completed by calling klp_free_patch_finish()
+ * outside klp_mutex.
+ */
+void klp_free_patch_start(struct klp_patch *patch)
{
- klp_free_objects_limited(patch, NULL);
if (!list_empty(&patch->list))
list_del(&patch->list);
+
+ klp_free_objects(patch);
+}
+
+/*
+ * This function implements the free part that must be called outside
+ * klp_mutex.
+ *
+ * It must be called after klp_free_patch_start(). And it has to be
+ * the last function accessing the livepatch structures when the patch
+ * gets disabled.
+ */
+static void klp_free_patch_finish(struct klp_patch *patch)
+{
+ /*
+ * Avoid deadlock with enabled_store() sysfs callback by
+ * calling this outside klp_mutex. It is safe because
+ * this is called when the patch gets disabled and it
+ * cannot get enabled again.
+ */
+ if (patch->kobj_added) {
+ kobject_put(&patch->kobj);
+ wait_for_completion(&patch->finish);
+ }
+
+ /* Put the module after the last access to struct klp_patch. */
+ if (!patch->forced)
+ module_put(patch->mod);
+}
+
+/*
+ * 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 int klp_init_func(struct klp_object *obj, struct klp_func *func)
{
- if (!func->old_name || !func->new_func)
+ int ret;
+
+ if (!func->old_name)
+ return -EINVAL;
+
+ /*
+ * NOPs get the address later. The patched module must be loaded,
+ * see klp_init_object_loaded().
+ */
+ if (!func->new_func && !func->nop)
return -EINVAL;
if (strlen(func->old_name) >= KSYM_NAME_LEN)
@@ -690,9 +724,13 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
* object. If the user selects 0 for old_sympos, then 1 will be used
* since a unique symbol will be the first occurrence.
*/
- return kobject_init_and_add(&func->kobj, &klp_ktype_func,
- &obj->kobj, "%s,%lu", func->old_name,
- func->old_sympos ? func->old_sympos : 1);
+ ret = kobject_init_and_add(&func->kobj, &klp_ktype_func,
+ &obj->kobj, "%s,%lu", func->old_name,
+ func->old_sympos ? func->old_sympos : 1);
+ if (!ret)
+ func->kobj_added = true;
+
+ return ret;
}
/* Arches may override this to finish any remaining arch-specific tasks */
@@ -721,11 +759,11 @@ static int klp_init_object_loaded(struct klp_patch *patch,
klp_for_each_func(obj, func) {
ret = klp_find_object_symbol(obj->name, func->old_name,
func->old_sympos,
- &func->old_addr);
+ (unsigned long *)&func->old_func);
if (ret)
return ret;
- ret = kallsyms_lookup_size_offset(func->old_addr,
+ ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
&func->old_size, NULL);
if (!ret) {
pr_err("kallsyms size lookup failed for '%s'\n",
@@ -733,6 +771,9 @@ static int klp_init_object_loaded(struct klp_patch *patch,
return -ENOENT;
}
+ if (func->nop)
+ func->new_func = func->old_func;
+
ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
&func->new_size, NULL);
if (!ret) {
@@ -751,9 +792,6 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
int ret;
const char *name;
- if (!obj->funcs)
- return -EINVAL;
-
if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
return -EINVAL;
@@ -767,122 +805,191 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
&patch->kobj, "%s", name);
if (ret)
return ret;
+ obj->kobj_added = true;
klp_for_each_func(obj, func) {
ret = klp_init_func(obj, func);
if (ret)
- goto free;
+ return ret;
}
- if (klp_is_object_loaded(obj)) {
+ if (klp_is_object_loaded(obj))
ret = klp_init_object_loaded(patch, obj);
- if (ret)
- goto free;
- }
- return 0;
-
-free:
- klp_free_funcs_limited(obj, func);
- kobject_put(&obj->kobj);
return ret;
}
-static int klp_init_patch(struct klp_patch *patch)
+static int klp_init_patch_early(struct klp_patch *patch)
{
struct klp_object *obj;
- int ret;
+ struct klp_func *func;
if (!patch->objs)
return -EINVAL;
- mutex_lock(&klp_mutex);
-
+ INIT_LIST_HEAD(&patch->list);
+ INIT_LIST_HEAD(&patch->obj_list);
+ patch->kobj_added = false;
patch->enabled = false;
+ patch->forced = false;
+ INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
init_completion(&patch->finish);
+ klp_for_each_object_static(patch, obj) {
+ if (!obj->funcs)
+ return -EINVAL;
+
+ INIT_LIST_HEAD(&obj->func_list);
+ obj->kobj_added = false;
+ list_add_tail(&obj->node, &patch->obj_list);
+
+ klp_for_each_func_static(obj, func) {
+ func->kobj_added = false;
+ list_add_tail(&func->node, &obj->func_list);
+ }
+ }
+
+ if (!try_module_get(patch->mod))
+ return -ENODEV;
+
+ return 0;
+}
+
+static int klp_init_patch(struct klp_patch *patch)
+{
+ struct klp_object *obj;
+ int ret;
+
ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
klp_root_kobj, "%s", patch->mod->name);
- if (ret) {
- mutex_unlock(&klp_mutex);
+ if (ret)
return ret;
+ patch->kobj_added = true;
+
+ if (patch->replace) {
+ ret = klp_add_nops(patch);
+ if (ret)
+ return ret;
}
klp_for_each_object(patch, obj) {
ret = klp_init_object(patch, obj);
if (ret)
- goto free;
+ return ret;
}
list_add_tail(&patch->list, &klp_patches);
- mutex_unlock(&klp_mutex);
-
return 0;
+}
-free:
- klp_free_objects_limited(patch, obj);
+static int __klp_disable_patch(struct klp_patch *patch)
+{
+ struct klp_object *obj;
- mutex_unlock(&klp_mutex);
+ if (WARN_ON(!patch->enabled))
+ return -EINVAL;
- kobject_put(&patch->kobj);
- wait_for_completion(&patch->finish);
+ if (klp_transition_patch)
+ return -EBUSY;
- return ret;
+ klp_init_transition(patch, KLP_UNPATCHED);
+
+ klp_for_each_object(patch, obj)
+ if (obj->patched)
+ klp_pre_unpatch_callback(obj);
+
+ /*
+ * Enforce the order of the func->transition writes in
+ * klp_init_transition() and the TIF_PATCH_PENDING writes in
+ * klp_start_transition(). In the rare case where klp_ftrace_handler()
+ * is called shortly after klp_update_patch_state() switches the task,
+ * this ensures the handler sees that func->transition is set.
+ */
+ smp_wmb();
+
+ klp_start_transition();
+ patch->enabled = false;
+ klp_try_complete_transition();
+
+ return 0;
}
-/**
- * klp_unregister_patch() - unregisters a patch
- * @patch: Disabled patch to be unregistered
- *
- * Frees the data structures and removes the sysfs interface.
- *
- * Return: 0 on success, otherwise error
- */
-int klp_unregister_patch(struct klp_patch *patch)
+static int __klp_enable_patch(struct klp_patch *patch)
{
+ struct klp_object *obj;
int ret;
- mutex_lock(&klp_mutex);
+ if (klp_transition_patch)
+ return -EBUSY;
- if (!klp_is_patch_registered(patch)) {
- ret = -EINVAL;
- goto err;
- }
+ if (WARN_ON(patch->enabled))
+ return -EINVAL;
- if (patch->enabled) {
- ret = -EBUSY;
- goto err;
- }
+ if (!patch->kobj_added)
+ return -EINVAL;
- klp_free_patch(patch);
+ pr_notice("enabling patch '%s'\n", patch->mod->name);
- mutex_unlock(&klp_mutex);
+ klp_init_transition(patch, KLP_PATCHED);
+
+ /*
+ * Enforce the order of the func->transition writes in
+ * klp_init_transition() and the ops->func_stack writes in
+ * klp_patch_object(), so that klp_ftrace_handler() will see the
+ * func->transition updates before the handler is registered and the
+ * new funcs become visible to the handler.
+ */
+ smp_wmb();
+
+ klp_for_each_object(patch, obj) {
+ if (!klp_is_object_loaded(obj))
+ continue;
+
+ ret = klp_pre_patch_callback(obj);
+ if (ret) {
+ pr_warn("pre-patch callback failed for object '%s'\n",
+ klp_is_module(obj) ? obj->name : "vmlinux");
+ goto err;
+ }
+
+ ret = klp_patch_object(obj);
+ if (ret) {
+ pr_warn("failed to patch object '%s'\n",
+ klp_is_module(obj) ? obj->name : "vmlinux");
+ goto err;
+ }
+ }
- kobject_put(&patch->kobj);
- wait_for_completion(&patch->finish);
+ klp_start_transition();
+ patch->enabled = true;
+ klp_try_complete_transition();
return 0;
err:
- mutex_unlock(&klp_mutex);
+ pr_warn("failed to enable patch '%s'\n", patch->mod->name);
+
+ klp_cancel_transition();
return ret;
}
-EXPORT_SYMBOL_GPL(klp_unregister_patch);
/**
- * klp_register_patch() - registers a patch
- * @patch: Patch to be registered
+ * klp_enable_patch() - enable the livepatch
+ * @patch: patch to be enabled
*
- * Initializes the data structure associated with the patch and
- * creates the sysfs interface.
+ * Initializes the data structure associated with the patch, creates the sysfs
+ * interface, performs the needed symbol lookups and code relocations,
+ * registers the patched functions with ftrace.
*
- * There is no need to take the reference on the patch module here. It is done
- * later when the patch is enabled.
+ * This function is supposed to be called from the livepatch module_init()
+ * callback.
*
* Return: 0 on success, otherwise error
*/
-int klp_register_patch(struct klp_patch *patch)
+int klp_enable_patch(struct klp_patch *patch)
{
+ int ret;
+
if (!patch || !patch->mod)
return -EINVAL;
@@ -897,12 +1004,91 @@ int klp_register_patch(struct klp_patch *patch)
if (!klp_have_reliable_stack()) {
pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
- return -ENOSYS;
+ return -EOPNOTSUPP;
+ }
+
+
+ mutex_lock(&klp_mutex);
+
+ ret = klp_init_patch_early(patch);
+ if (ret) {
+ mutex_unlock(&klp_mutex);
+ return ret;
}
- return klp_init_patch(patch);
+ ret = klp_init_patch(patch);
+ if (ret)
+ goto err;
+
+ ret = __klp_enable_patch(patch);
+ if (ret)
+ goto err;
+
+ mutex_unlock(&klp_mutex);
+
+ return 0;
+
+err:
+ klp_free_patch_start(patch);
+
+ mutex_unlock(&klp_mutex);
+
+ klp_free_patch_finish(patch);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(klp_enable_patch);
+
+/*
+ * This function removes replaced patches.
+ *
+ * We could be pretty aggressive here. It is called in the situation where
+ * these structures are no longer accessible. All functions are redirected
+ * by the klp_transition_patch. They use either a new code or they are in
+ * the original code because of the special nop function patches.
+ *
+ * The only exception is when the transition was forced. In this case,
+ * klp_ftrace_handler() might still see the replaced patch on the stack.
+ * Fortunately, it is carefully designed to work with removed functions
+ * thanks to RCU. We only have to keep the patches on the system. Also
+ * this is handled transparently by patch->module_put.
+ */
+void klp_discard_replaced_patches(struct klp_patch *new_patch)
+{
+ struct klp_patch *old_patch, *tmp_patch;
+
+ klp_for_each_patch_safe(old_patch, tmp_patch) {
+ if (old_patch == new_patch)
+ return;
+
+ old_patch->enabled = false;
+ klp_unpatch_objects(old_patch);
+ klp_free_patch_start(old_patch);
+ schedule_work(&old_patch->free_work);
+ }
+}
+
+/*
+ * This function removes the dynamically allocated 'nop' functions.
+ *
+ * We could be pretty aggressive. NOPs do not change the existing
+ * behavior except for adding unnecessary delay by the ftrace handler.
+ *
+ * It is safe even when the transition was forced. The ftrace handler
+ * will see a valid ops->func_stack entry thanks to RCU.
+ *
+ * We could even free the NOPs structures. They must be the last entry
+ * in ops->func_stack. Therefore unregister_ftrace_function() is called.
+ * It does the same as klp_synchronize_transition() to make sure that
+ * nobody is inside the ftrace handler once the operation finishes.
+ *
+ * IMPORTANT: It must be called right after removing the replaced patches!
+ */
+void klp_discard_nops(struct klp_patch *new_patch)
+{
+ klp_unpatch_objects_dynamic(klp_transition_patch);
+ klp_free_objects_dynamic(klp_transition_patch);
}
-EXPORT_SYMBOL_GPL(klp_register_patch);
/*
* Remove parts of patches that touch a given kernel module. The list of
@@ -915,7 +1101,7 @@ static void klp_cleanup_module_patches_limited(struct module *mod,
struct klp_patch *patch;
struct klp_object *obj;
- list_for_each_entry(patch, &klp_patches, list) {
+ klp_for_each_patch(patch) {
if (patch == limit)
break;
@@ -923,21 +1109,14 @@ static void klp_cleanup_module_patches_limited(struct module *mod,
if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
continue;
- /*
- * Only unpatch the module if the patch is enabled or
- * is in transition.
- */
- if (patch->enabled || patch == klp_transition_patch) {
+ if (patch != klp_transition_patch)
+ klp_pre_unpatch_callback(obj);
- if (patch != klp_transition_patch)
- klp_pre_unpatch_callback(obj);
+ pr_notice("reverting patch '%s' on unloading module '%s'\n",
+ patch->mod->name, obj->mod->name);
+ klp_unpatch_object(obj);
- pr_notice("reverting patch '%s' on unloading module '%s'\n",
- patch->mod->name, obj->mod->name);
- klp_unpatch_object(obj);
-
- klp_post_unpatch_callback(obj);
- }
+ klp_post_unpatch_callback(obj);
klp_free_object_loaded(obj);
break;
@@ -962,7 +1141,7 @@ int klp_module_coming(struct module *mod)
*/
mod->klp_alive = true;
- list_for_each_entry(patch, &klp_patches, list) {
+ klp_for_each_patch(patch) {
klp_for_each_object(patch, obj) {
if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
continue;
@@ -976,13 +1155,6 @@ int klp_module_coming(struct module *mod)
goto err;
}
- /*
- * Only patch the module if the patch is enabled or is
- * in transition.
- */
- if (!patch->enabled && patch != klp_transition_patch)
- break;
-
pr_notice("applying patch '%s' to loading module '%s'\n",
patch->mod->name, obj->mod->name);
diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h
index 48a83d4364cf..ec43a40b853f 100644
--- a/kernel/livepatch/core.h
+++ b/kernel/livepatch/core.h
@@ -5,6 +5,17 @@
#include <linux/livepatch.h>
extern struct mutex klp_mutex;
+extern struct list_head klp_patches;
+
+#define klp_for_each_patch_safe(patch, tmp_patch) \
+ list_for_each_entry_safe(patch, tmp_patch, &klp_patches, list)
+
+#define klp_for_each_patch(patch) \
+ list_for_each_entry(patch, &klp_patches, list)
+
+void klp_free_patch_start(struct klp_patch *patch);
+void klp_discard_replaced_patches(struct klp_patch *new_patch);
+void klp_discard_nops(struct klp_patch *new_patch);
static inline bool klp_is_object_loaded(struct klp_object *obj)
{
diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
index 7702cb4064fc..99cb3ad05eb4 100644
--- a/kernel/livepatch/patch.c
+++ b/kernel/livepatch/patch.c
@@ -34,7 +34,7 @@
static LIST_HEAD(klp_ops);
-struct klp_ops *klp_find_ops(unsigned long old_addr)
+struct klp_ops *klp_find_ops(void *old_func)
{
struct klp_ops *ops;
struct klp_func *func;
@@ -42,7 +42,7 @@ struct klp_ops *klp_find_ops(unsigned long old_addr)
list_for_each_entry(ops, &klp_ops, node) {
func = list_first_entry(&ops->func_stack, struct klp_func,
stack_node);
- if (func->old_addr == old_addr)
+ if (func->old_func == old_func)
return ops;
}
@@ -118,7 +118,15 @@ static void notrace klp_ftrace_handler(unsigned long ip,
}
}
+ /*
+ * NOPs are used to replace existing patches with original code.
+ * Do nothing! Setting pc would cause an infinite loop.
+ */
+ if (func->nop)
+ goto unlock;
+
klp_arch_set_pc(regs, (unsigned long)func->new_func);
+
unlock:
preempt_enable_notrace();
}
@@ -142,17 +150,18 @@ static void klp_unpatch_func(struct klp_func *func)
if (WARN_ON(!func->patched))
return;
- if (WARN_ON(!func->old_addr))
+ if (WARN_ON(!func->old_func))
return;
- ops = klp_find_ops(func->old_addr);
+ ops = klp_find_ops(func->old_func);
if (WARN_ON(!ops))
return;
if (list_is_singular(&ops->func_stack)) {
unsigned long ftrace_loc;
- ftrace_loc = klp_get_ftrace_location(func->old_addr);
+ ftrace_loc =
+ klp_get_ftrace_location((unsigned long)func->old_func);
if (WARN_ON(!ftrace_loc))
return;
@@ -174,17 +183,18 @@ static int klp_patch_func(struct klp_func *func)
struct klp_ops *ops;
int ret;
- if (WARN_ON(!func->old_addr))
+ if (WARN_ON(!func->old_func))
return -EINVAL;
if (WARN_ON(func->patched))
return -EINVAL;
- ops = klp_find_ops(func->old_addr);
+ ops = klp_find_ops(func->old_func);
if (!ops) {
unsigned long ftrace_loc;
- ftrace_loc = klp_get_ftrace_location(func->old_addr);
+ ftrace_loc =
+ klp_get_ftrace_location((unsigned long)func->old_func);
if (!ftrace_loc) {
pr_err("failed to find location for function '%s'\n",
func->old_name);
@@ -236,15 +246,26 @@ err:
return ret;
}
-void klp_unpatch_object(struct klp_object *obj)
+static void __klp_unpatch_object(struct klp_object *obj, bool nops_only)
{
struct klp_func *func;
- klp_for_each_func(obj, func)
+ klp_for_each_func(obj, func) {
+ if (nops_only && !func->nop)
+ continue;
+
if (func->patched)
klp_unpatch_func(func);
+ }
- obj->patched = false;
+ if (obj->dynamic || !nops_only)
+ obj->patched = false;
+}
+
+
+void klp_unpatch_object(struct klp_object *obj)
+{
+ __klp_unpatch_object(obj, false);
}
int klp_patch_object(struct klp_object *obj)
@@ -267,11 +288,21 @@ int klp_patch_object(struct klp_object *obj)
return 0;
}
-void klp_unpatch_objects(struct klp_patch *patch)
+static void __klp_unpatch_objects(struct klp_patch *patch, bool nops_only)
{
struct klp_object *obj;
klp_for_each_object(patch, obj)
if (obj->patched)
- klp_unpatch_object(obj);
+ __klp_unpatch_object(obj, nops_only);
+}
+
+void klp_unpatch_objects(struct klp_patch *patch)
+{
+ __klp_unpatch_objects(patch, false);
+}
+
+void klp_unpatch_objects_dynamic(struct klp_patch *patch)
+{
+ __klp_unpatch_objects(patch, true);
}
diff --git a/kernel/livepatch/patch.h b/kernel/livepatch/patch.h
index e72d8250d04b..d5f2fbe373e0 100644
--- a/kernel/livepatch/patch.h
+++ b/kernel/livepatch/patch.h
@@ -10,7 +10,7 @@
* struct klp_ops - structure for tracking registered ftrace ops structs
*
* A single ftrace_ops is shared between all enabled replacement functions
- * (klp_func structs) which have the same old_addr. This allows the switch
+ * (klp_func structs) which have the same old_func. This allows the switch
* between function versions to happen instantaneously by updating the klp_ops
* struct's func_stack list. The winner is the klp_func at the top of the
* func_stack (front of the list).
@@ -25,10 +25,11 @@ struct klp_ops {
struct ftrace_ops fops;
};
-struct klp_ops *klp_find_ops(unsigned long old_addr);
+struct klp_ops *klp_find_ops(void *old_func);
int klp_patch_object(struct klp_object *obj);
void klp_unpatch_object(struct klp_object *obj);
void klp_unpatch_objects(struct klp_patch *patch);
+void klp_unpatch_objects_dynamic(struct klp_patch *patch);
#endif /* _LIVEPATCH_PATCH_H */
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 304d5eb8a98c..9c89ae8b337a 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -29,11 +29,13 @@
#define MAX_STACK_ENTRIES 100
#define STACK_ERR_BUF_SIZE 128
+#define SIGNALS_TIMEOUT 15
+
struct klp_patch *klp_transition_patch;
static int klp_target_state = KLP_UNDEFINED;
-static bool klp_forced = false;
+static unsigned int klp_signals_cnt;
/*
* This work can be performed periodically to finish patching or unpatching any
@@ -87,6 +89,11 @@ static void klp_complete_transition(void)
klp_transition_patch->mod->name,
klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
+ if (klp_transition_patch->replace && klp_target_state == KLP_PATCHED) {
+ klp_discard_replaced_patches(klp_transition_patch);
+ klp_discard_nops(klp_transition_patch);
+ }
+
if (klp_target_state == KLP_UNPATCHED) {
/*
* All tasks have transitioned to KLP_UNPATCHED so we can now
@@ -136,13 +143,6 @@ static void klp_complete_transition(void)
pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name,
klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
- /*
- * klp_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)
- module_put(klp_transition_patch->mod);
-
klp_target_state = KLP_UNDEFINED;
klp_transition_patch = NULL;
}
@@ -224,11 +224,11 @@ static int klp_check_stack_func(struct klp_func *func,
* Check for the to-be-patched function
* (the previous func).
*/
- ops = klp_find_ops(func->old_addr);
+ ops = klp_find_ops(func->old_func);
if (list_is_singular(&ops->func_stack)) {
/* original function */
- func_addr = func->old_addr;
+ func_addr = (unsigned long)func->old_func;
func_size = func->old_size;
} else {
/* previously patched function */
@@ -348,6 +348,47 @@ done:
}
/*
+ * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set.
+ * Kthreads with TIF_PATCH_PENDING set are woken up.
+ */
+static void klp_send_signals(void)
+{
+ struct task_struct *g, *task;
+
+ if (klp_signals_cnt == SIGNALS_TIMEOUT)
+ pr_notice("signaling remaining tasks\n");
+
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, task) {
+ if (!klp_patch_pending(task))
+ continue;
+
+ /*
+ * There is a small race here. We could see TIF_PATCH_PENDING
+ * set and decide to wake up a kthread or send a fake signal.
+ * Meanwhile the task could migrate itself and the action
+ * would be meaningless. It is not serious though.
+ */
+ if (task->flags & PF_KTHREAD) {
+ /*
+ * Wake up a kthread which sleeps interruptedly and
+ * still has not been migrated.
+ */
+ wake_up_state(task, TASK_INTERRUPTIBLE);
+ } else {
+ /*
+ * Send fake signal to all non-kthread tasks which are
+ * still not migrated.
+ */
+ spin_lock_irq(&task->sighand->siglock);
+ signal_wake_up(task, 0);
+ spin_unlock_irq(&task->sighand->siglock);
+ }
+ }
+ read_unlock(&tasklist_lock);
+}
+
+/*
* Try to switch all remaining tasks to the target patch state by walking the
* stacks of sleeping tasks and looking for any to-be-patched or
* to-be-unpatched functions. If such functions are found, the task can't be
@@ -359,6 +400,7 @@ void klp_try_complete_transition(void)
{
unsigned int cpu;
struct task_struct *g, *task;
+ struct klp_patch *patch;
bool complete = true;
WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED);
@@ -396,6 +438,10 @@ void klp_try_complete_transition(void)
put_online_cpus();
if (!complete) {
+ if (klp_signals_cnt && !(klp_signals_cnt % SIGNALS_TIMEOUT))
+ klp_send_signals();
+ klp_signals_cnt++;
+
/*
* Some tasks weren't able to be switched over. Try again
* later and/or wait for other methods like kernel exit
@@ -407,7 +453,18 @@ void klp_try_complete_transition(void)
}
/* we're done, now cleanup the data structures */
+ patch = klp_transition_patch;
klp_complete_transition();
+
+ /*
+ * It would make more sense to free the patch in
+ * klp_complete_transition() but it is called also
+ * from klp_cancel_transition().
+ */
+ if (!patch->enabled) {
+ klp_free_patch_start(patch);
+ schedule_work(&patch->free_work);
+ }
}
/*
@@ -446,6 +503,8 @@ void klp_start_transition(void)
if (task->patch_state != klp_target_state)
set_tsk_thread_flag(task, TIF_PATCH_PENDING);
}
+
+ klp_signals_cnt = 0;
}
/*
@@ -569,47 +628,6 @@ void klp_copy_process(struct task_struct *child)
}
/*
- * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set.
- * Kthreads with TIF_PATCH_PENDING set are woken up. Only admin can request this
- * action currently.
- */
-void klp_send_signals(void)
-{
- struct task_struct *g, *task;
-
- pr_notice("signaling remaining tasks\n");
-
- read_lock(&tasklist_lock);
- for_each_process_thread(g, task) {
- if (!klp_patch_pending(task))
- continue;
-
- /*
- * There is a small race here. We could see TIF_PATCH_PENDING
- * set and decide to wake up a kthread or send a fake signal.
- * Meanwhile the task could migrate itself and the action
- * would be meaningless. It is not serious though.
- */
- if (task->flags & PF_KTHREAD) {
- /*
- * Wake up a kthread which sleeps interruptedly and
- * still has not been migrated.
- */
- wake_up_state(task, TASK_INTERRUPTIBLE);
- } else {
- /*
- * Send fake signal to all non-kthread tasks which are
- * still not migrated.
- */
- spin_lock_irq(&task->sighand->siglock);
- signal_wake_up(task, 0);
- spin_unlock_irq(&task->sighand->siglock);
- }
- }
- read_unlock(&tasklist_lock);
-}
-
-/*
* Drop TIF_PATCH_PENDING of all tasks on admin's request. This forces an
* existing transition to finish.
*
@@ -620,6 +638,7 @@ void klp_send_signals(void)
*/
void klp_force_transition(void)
{
+ struct klp_patch *patch;
struct task_struct *g, *task;
unsigned int cpu;
@@ -633,5 +652,6 @@ void klp_force_transition(void)
for_each_possible_cpu(cpu)
klp_update_patch_state(idle_task(cpu));
- klp_forced = true;
+ klp_for_each_patch(patch)
+ patch->forced = true;
}
diff --git a/kernel/livepatch/transition.h b/kernel/livepatch/transition.h
index f9d0bc016067..322db16233de 100644
--- a/kernel/livepatch/transition.h
+++ b/kernel/livepatch/transition.h
@@ -11,7 +11,6 @@ void klp_cancel_transition(void);
void klp_start_transition(void);
void klp_try_complete_transition(void);
void klp_reverse_transition(void);
-void klp_send_signals(void);
void klp_force_transition(void);
#endif /* _LIVEPATCH_TRANSITION_H */