[PATCH v2 0/2] Livepatch module notifier cleanup

[PATCH v2 0/2] Livepatch module notifier cleanup

[Jessica Yu]

These are the remaining 2 patches that came from the original ftrace/livepatch
module notifier patchset found here: https://lkml.org/lkml/2016/2/8/1180

Basically, the patchset does a bit of module.c cleanup (patch 1) in
preparation for the klp_module_{coming,going} calls (patch 2). We decided
to stop relying on the module notifier callchain in favor of hard-coding
the appropriate livepatch function calls that handle coming and going
modules. Hard-coding these calls will guarantee that ftrace and livepatch
exit/initialization routines are called in the correct order without
relying on module notifiers.

The patches should be nearly exactly the same as those from the previous
discussion, except in patch 2 I've added back the #if IS_ENABLED(CONFIG_LIVEPATCH)
guard in livepatch.h.

Patches based on linux-next.

Previous discussion (v4) found here: https://lkml.org/lkml/2016/2/8/1180

v2:
  - we don't need to change mod->state to GOING when cleaning up during
    failed module load
  - modify mod->state check to allow klp_module_going() to be called in
    both COMING and GOING states

Jessica Yu (2):
  modules: split part of complete_formation() into prepare_coming_module()
  livepatch/module: remove livepatch module notifier

 include/linux/livepatch.h |  13 ++++
 kernel/livepatch/core.c   | 147 ++++++++++++++++++++++------------------------
 kernel/module.c           |  36 +++++++++---
 3 files changed, 112 insertions(+), 84 deletions(-)

-- 
2.4.3

[PATCH v2 1/2] modules: split part of complete_formation() into prepare_coming_module()

[Jessica Yu]

Put all actions in complete_formation() that are performed after
module->state is set to MODULE_STATE_COMING into a separate function
prepare_coming_module(). This split prepares for the removal of the
livepatch module notifiers in favor of hard-coding function calls to
klp_module_{coming,going} in the module loader.

The complete_formation -> prepare_coming_module split will also make error
handling easier since we can jump to the appropriate error label to do any
module GOING cleanup after all the COMING-actions have completed.

Signed-off-by: Jessica Yu <jeyu@redhat.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
---
 kernel/module.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 87cfeb2..1981ae0 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3312,6 +3312,14 @@ out_unlocked:
 	return err;
 }
 
+static int prepare_coming_module(struct module *mod)
+{
+	ftrace_module_enable(mod);
+	blocking_notifier_call_chain(&module_notify_list,
+				     MODULE_STATE_COMING, mod);
+	return 0;
+}
+
 static int complete_formation(struct module *mod, struct load_info *info)
 {
 	int err;
@@ -3335,9 +3343,6 @@ static int complete_formation(struct module *mod, struct load_info *info)
 	mod->state = MODULE_STATE_COMING;
 	mutex_unlock(&module_mutex);
 
-	ftrace_module_enable(mod);
-	blocking_notifier_call_chain(&module_notify_list,
-				     MODULE_STATE_COMING, mod);
 	return 0;
 
 out:
@@ -3459,13 +3464,17 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	if (err)
 		goto ddebug_cleanup;
 
+	err = prepare_coming_module(mod);
+	if (err)
+		goto bug_cleanup;
+
 	/* Module is ready to execute: parsing args may do that. */
 	after_dashes = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
 				  -32768, 32767, mod,
 				  unknown_module_param_cb);
 	if (IS_ERR(after_dashes)) {
 		err = PTR_ERR(after_dashes);
-		goto bug_cleanup;
+		goto coming_cleanup;
 	} else if (after_dashes) {
 		pr_warn("%s: parameters '%s' after `--' ignored\n",
 		       mod->name, after_dashes);
@@ -3474,7 +3483,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	/* Link in to syfs. */
 	err = mod_sysfs_setup(mod, info, mod->kp, mod->num_kp);
 	if (err < 0)
-		goto bug_cleanup;
+		goto coming_cleanup;
 
 	/* Get rid of temporary copy. */
 	free_copy(info);
@@ -3484,15 +3493,16 @@ static int load_module(struct load_info *info, const char __user *uargs,
 
 	return do_init_module(mod);
 
+ coming_cleanup:
+	blocking_notifier_call_chain(&module_notify_list,
+				     MODULE_STATE_GOING, mod);
+
  bug_cleanup:
 	/* module_bug_cleanup needs module_mutex protection */
 	mutex_lock(&module_mutex);
 	module_bug_cleanup(mod);
 	mutex_unlock(&module_mutex);
 
-	blocking_notifier_call_chain(&module_notify_list,
-				     MODULE_STATE_GOING, mod);
-
 	/* we can't deallocate the module until we clear memory protection */
 	module_disable_ro(mod);
 	module_disable_nx(mod);
-- 
2.4.3

Re: [PATCH v2 1/2] modules: split part of complete_formation() into prepare_coming_module()

[Petr Mladek]

On Fri 2016-03-11 15:03:47, Jessica Yu wrote:
> Put all actions in complete_formation() that are performed after
> module->state is set to MODULE_STATE_COMING into a separate function
> prepare_coming_module(). This split prepares for the removal of the
> livepatch module notifiers in favor of hard-coding function calls to
> klp_module_{coming,going} in the module loader.
> 
> The complete_formation -> prepare_coming_module split will also make error
> handling easier since we can jump to the appropriate error label to do any
> module GOING cleanup after all the COMING-actions have completed.
> 
> Signed-off-by: Jessica Yu <jeyu@redhat.com>
> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Acked-by: Rusty Russell <rusty@rustcorp.com.au>
> ---
>  kernel/module.c | 26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index 87cfeb2..1981ae0 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3312,6 +3312,14 @@ out_unlocked:
>  	return err;
>  }
>  
> +static int prepare_coming_module(struct module *mod)
> +{
> +	ftrace_module_enable(mod);
> +	blocking_notifier_call_chain(&module_notify_list,
> +				     MODULE_STATE_COMING, mod);
> +	return 0;
> +}

Nit, just in case you send a new version. Please, move this below
complete_formation(). It is nice when the funtions are defined
in the same order as they are called :-)

It is a cosmetic change and it should not invalidate other acks.

In each case, the patch looks fine:

Reviewed-by: Petr Mladek <pmladek@suse.cz>

Best Regards,
Petr

[PATCH v2 2/2] livepatch/module: remove livepatch module notifier

[Jessica Yu]

Remove the livepatch module notifier in favor of directly enabling and
disabling patches to modules in the module loader. Hard-coding the
function calls ensures that ftrace_module_enable() is run before
klp_module_coming() during module load, and that klp_module_going() is
run before ftrace_release_mod() during module unload. This way, ftrace
and livepatch code is run in the correct order during the module
load/unload sequence without dependence on the module notifier call chain.

Signed-off-by: Jessica Yu <jeyu@redhat.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
---
 include/linux/livepatch.h |  13 ++++
 kernel/livepatch/core.c   | 147 ++++++++++++++++++++++------------------------
 kernel/module.c           |  10 ++++
 3 files changed, 94 insertions(+), 76 deletions(-)

diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index c056797..bd830d5 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -24,6 +24,8 @@
 #include <linux/module.h>
 #include <linux/ftrace.h>
 
+#if IS_ENABLED(CONFIG_LIVEPATCH)
+
 #include <asm/livepatch.h>
 
 enum klp_state {
@@ -132,4 +134,15 @@ int klp_unregister_patch(struct klp_patch *);
 int klp_enable_patch(struct klp_patch *);
 int klp_disable_patch(struct klp_patch *);
 
+/* Called from the module loader during module coming/going states */
+int klp_module_coming(struct module *mod);
+void klp_module_going(struct module *mod);
+
+#else /* !CONFIG_LIVEPATCH */
+
+static inline int klp_module_coming(struct module *mod) { return 0; }
+static inline void klp_module_going(struct module *mod) { }
+
+#endif /* CONFIG_LIVEPATCH */
+
 #endif /* _LINUX_LIVEPATCH_H_ */
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 780f00c..4fafbae 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -99,12 +99,12 @@ static void klp_find_object_module(struct klp_object *obj)
 	/*
 	 * We do not want to block removal of patched modules and therefore
 	 * we do not take a reference here. The patches are removed by
-	 * a going module handler instead.
+	 * klp_module_going() instead.
 	 */
 	mod = find_module(obj->name);
 	/*
-	 * Do not mess work of the module coming and going notifiers.
-	 * Note that the patch might still be needed before the going handler
+	 * Do not mess work of klp_module_coming() and klp_module_going().
+	 * Note that the patch might still be needed before klp_module_going()
 	 * is called. Module functions can be called even in the GOING state
 	 * until mod->exit() finishes. This is especially important for
 	 * patches that modify semantic of the functions.
@@ -866,103 +866,108 @@ int klp_register_patch(struct klp_patch *patch)
 }
 EXPORT_SYMBOL_GPL(klp_register_patch);
 
-static int klp_module_notify_coming(struct klp_patch *patch,
-				     struct klp_object *obj)
+int klp_module_coming(struct module *mod)
 {
-	struct module *pmod = patch->mod;
-	struct module *mod = obj->mod;
 	int ret;
+	struct klp_patch *patch;
+	struct klp_object *obj;
 
-	ret = klp_init_object_loaded(patch, obj);
-	if (ret) {
-		pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
-			pmod->name, mod->name, ret);
-		return ret;
-	}
+	if (WARN_ON(mod->state != MODULE_STATE_COMING))
+		return -EINVAL;
 
-	if (patch->state == KLP_DISABLED)
-		return 0;
+	mutex_lock(&klp_mutex);
+	/*
+	 * Each module has to know that klp_module_coming()
+	 * has been called. We never know what module will
+	 * get patched by a new patch.
+	 */
+	mod->klp_alive = true;
 
-	pr_notice("applying patch '%s' to loading module '%s'\n",
-		  pmod->name, mod->name);
+	list_for_each_entry(patch, &klp_patches, list) {
+		klp_for_each_object(patch, obj) {
+			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
+				continue;
 
-	ret = klp_enable_object(obj);
-	if (ret)
-		pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
-			pmod->name, mod->name, ret);
-	return ret;
-}
+			obj->mod = mod;
 
-static void klp_module_notify_going(struct klp_patch *patch,
-				    struct klp_object *obj)
-{
-	struct module *pmod = patch->mod;
-	struct module *mod = obj->mod;
+			ret = klp_init_object_loaded(patch, obj);
+			if (ret) {
+				pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
+					patch->mod->name, obj->mod->name, ret);
+				goto err;
+			}
 
-	if (patch->state == KLP_DISABLED)
-		goto disabled;
+			if (patch->state == KLP_DISABLED)
+				break;
+
+			pr_notice("applying patch '%s' to loading module '%s'\n",
+				  patch->mod->name, obj->mod->name);
+
+			ret = klp_enable_object(obj);
+			if (ret) {
+				pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
+					patch->mod->name, obj->mod->name, ret);
+				goto err;
+			}
+
+			break;
+		}
+	}
 
-	pr_notice("reverting patch '%s' on unloading module '%s'\n",
-		  pmod->name, mod->name);
+	mutex_unlock(&klp_mutex);
 
-	klp_disable_object(obj);
+	return 0;
 
-disabled:
+err:
+	/*
+	 * If a patch is unsuccessfully applied, return
+	 * error to the module loader.
+	 */
+	pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
+		patch->mod->name, obj->mod->name, obj->mod->name);
 	klp_free_object_loaded(obj);
+	mutex_unlock(&klp_mutex);
+
+	return ret;
 }
 
-static int klp_module_notify(struct notifier_block *nb, unsigned long action,
-			     void *data)
+/* Module can be either COMING or GOING */
+void klp_module_going(struct module *mod)
 {
-	int ret;
-	struct module *mod = data;
 	struct klp_patch *patch;
 	struct klp_object *obj;
 
-	if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
-		return 0;
+	if (WARN_ON(mod->state != MODULE_STATE_GOING &&
+		    mod->state != MODULE_STATE_COMING))
+		return;
 
 	mutex_lock(&klp_mutex);
-
 	/*
-	 * Each module has to know that the notifier has been called.
-	 * We never know what module will get patched by a new patch.
+	 * Each module has to know that klp_module_going()
+	 * has been called. We never know what module will
+	 * get patched by a new patch.
 	 */
-	if (action == MODULE_STATE_COMING)
-		mod->klp_alive = true;
-	else /* MODULE_STATE_GOING */
-		mod->klp_alive = false;
+	mod->klp_alive = false;
 
 	list_for_each_entry(patch, &klp_patches, list) {
 		klp_for_each_object(patch, obj) {
 			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 				continue;
 
-			if (action == MODULE_STATE_COMING) {
-				obj->mod = mod;
-				ret = klp_module_notify_coming(patch, obj);
-				if (ret) {
-					obj->mod = NULL;
-					pr_warn("patch '%s' is in an inconsistent state!\n",
-						patch->mod->name);
-				}
-			} else /* MODULE_STATE_GOING */
-				klp_module_notify_going(patch, obj);
+			if (patch->state != KLP_DISABLED) {
+				pr_notice("reverting patch '%s' on unloading module '%s'\n",
+					  patch->mod->name, obj->mod->name);
+				klp_disable_object(obj);
+			}
 
+			klp_free_object_loaded(obj);
 			break;
 		}
 	}
 
 	mutex_unlock(&klp_mutex);
-
-	return 0;
 }
 
-static struct notifier_block klp_module_nb = {
-	.notifier_call = klp_module_notify,
-	.priority = INT_MIN+1, /* called late but before ftrace notifier */
-};
-
 static int __init klp_init(void)
 {
 	int ret;
@@ -973,21 +978,11 @@ static int __init klp_init(void)
 		return -EINVAL;
 	}
 
-	ret = register_module_notifier(&klp_module_nb);
-	if (ret)
-		return ret;
-
 	klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
-	if (!klp_root_kobj) {
-		ret = -ENOMEM;
-		goto unregister;
-	}
+	if (!klp_root_kobj)
+		return -ENOMEM;
 
 	return 0;
-
-unregister:
-	unregister_module_notifier(&klp_module_nb);
-	return ret;
 }
 
 module_init(klp_init);
diff --git a/kernel/module.c b/kernel/module.c
index 1981ae0..932fb35 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -53,6 +53,7 @@
 #include <asm/sections.h>
 #include <linux/tracepoint.h>
 #include <linux/ftrace.h>
+#include <linux/livepatch.h>
 #include <linux/async.h>
 #include <linux/percpu.h>
 #include <linux/kmemleak.h>
@@ -984,6 +985,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
 		mod->exit();
 	blocking_notifier_call_chain(&module_notify_list,
 				     MODULE_STATE_GOING, mod);
+	klp_module_going(mod);
 	ftrace_release_mod(mod);
 
 	async_synchronize_full();
@@ -3258,6 +3260,7 @@ fail:
 	module_put(mod);
 	blocking_notifier_call_chain(&module_notify_list,
 				     MODULE_STATE_GOING, mod);
+	klp_module_going(mod);
 	ftrace_release_mod(mod);
 	free_module(mod);
 	wake_up_all(&module_wq);
@@ -3314,7 +3317,13 @@ out_unlocked:
 
 static int prepare_coming_module(struct module *mod)
 {
+	int err;
+
 	ftrace_module_enable(mod);
+	err = klp_module_coming(mod);
+	if (err)
+		return err;
+
 	blocking_notifier_call_chain(&module_notify_list,
 				     MODULE_STATE_COMING, mod);
 	return 0;
@@ -3496,6 +3505,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
  coming_cleanup:
 	blocking_notifier_call_chain(&module_notify_list,
 				     MODULE_STATE_GOING, mod);
+	klp_module_going(mod);
 
  bug_cleanup:
 	/* module_bug_cleanup needs module_mutex protection */
-- 
2.4.3

Re: [PATCH v2 2/2] livepatch/module: remove livepatch module notifier

[Petr Mladek]

On Fri 2016-03-11 15:03:48, Jessica Yu wrote:
> Remove the livepatch module notifier in favor of directly enabling and
> disabling patches to modules in the module loader. Hard-coding the
> function calls ensures that ftrace_module_enable() is run before
> klp_module_coming() during module load, and that klp_module_going() is
> run before ftrace_release_mod() during module unload. This way, ftrace
> and livepatch code is run in the correct order during the module
> load/unload sequence without dependence on the module notifier call chain.
> 
> Signed-off-by: Jessica Yu <jeyu@redhat.com>
> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Acked-by: Rusty Russell <rusty@rustcorp.com.au>
> ---
>  include/linux/livepatch.h |  13 ++++
>  kernel/livepatch/core.c   | 147 ++++++++++++++++++++++------------------------
>  kernel/module.c           |  10 ++++
>  3 files changed, 94 insertions(+), 76 deletions(-)
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 780f00c..4fafbae 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -866,103 +866,108 @@ int klp_register_patch(struct klp_patch *patch)
>  }
>  EXPORT_SYMBOL_GPL(klp_register_patch);
>  
> -static int klp_module_notify_coming(struct klp_patch *patch,
> -				     struct klp_object *obj)
> +int klp_module_coming(struct module *mod)
>  {
> -	struct module *pmod = patch->mod;
> -	struct module *mod = obj->mod;
>  	int ret;
> +	struct klp_patch *patch;
> +	struct klp_object *obj;
>  
> -	ret = klp_init_object_loaded(patch, obj);
> -	if (ret) {
> -		pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
> -			pmod->name, mod->name, ret);
> -		return ret;
> -	}
> +	if (WARN_ON(mod->state != MODULE_STATE_COMING))
> +		return -EINVAL;
>  
> -	if (patch->state == KLP_DISABLED)
> -		return 0;
> +	mutex_lock(&klp_mutex);
> +	/*
> +	 * Each module has to know that klp_module_coming()
> +	 * has been called. We never know what module will
> +	 * get patched by a new patch.
> +	 */
> +	mod->klp_alive = true;
>  
> -	pr_notice("applying patch '%s' to loading module '%s'\n",
> -		  pmod->name, mod->name);
> +	list_for_each_entry(patch, &klp_patches, list) {
> +		klp_for_each_object(patch, obj) {
> +			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
> +				continue;
>  
> -	ret = klp_enable_object(obj);
> -	if (ret)
> -		pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
> -			pmod->name, mod->name, ret);
> -	return ret;
> -}
> +			obj->mod = mod;
>  
> -static void klp_module_notify_going(struct klp_patch *patch,
> -				    struct klp_object *obj)
> -{
> -	struct module *pmod = patch->mod;
> -	struct module *mod = obj->mod;
> +			ret = klp_init_object_loaded(patch, obj);
> +			if (ret) {
> +				pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
> +					patch->mod->name, obj->mod->name, ret);
> +				goto err;
> +			}
>  
> -	if (patch->state == KLP_DISABLED)
> -		goto disabled;
> +			if (patch->state == KLP_DISABLED)
> +				break;
> +
> +			pr_notice("applying patch '%s' to loading module '%s'\n",
> +				  patch->mod->name, obj->mod->name);
> +
> +			ret = klp_enable_object(obj);
> +			if (ret) {
> +				pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
> +					patch->mod->name, obj->mod->name, ret);
> +				goto err;
> +			}
> +
> +			break;
> +		}
> +	}
>  
> -	pr_notice("reverting patch '%s' on unloading module '%s'\n",
> -		  pmod->name, mod->name);
> +	mutex_unlock(&klp_mutex);
>  
> -	klp_disable_object(obj);
> +	return 0;
>  
> -disabled:
> +err:
> +	/*
> +	 * If a patch is unsuccessfully applied, return
> +	 * error to the module loader.
> +	 */
> +	pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
> +		patch->mod->name, obj->mod->name, obj->mod->name);

One more thing. We should add here:

	mod->klp_alive = true;

Otherwise, there is a small race window when a new patch will try to
patch the module.

>  	klp_free_object_loaded(obj);
> +	mutex_unlock(&klp_mutex);
> +
> +	return ret;
>  }

With the above fix:

Reviewed-by: Petr Mladek <pmladek@suse.cz>


Best Regards,
Petr

Re: livepatch/module: remove livepatch module notifier

[Jessica Yu]

+++ Petr Mladek [14/03/16 16:06 +0100]:
>On Fri 2016-03-11 15:03:48, Jessica Yu wrote:
>> Remove the livepatch module notifier in favor of directly enabling and
>> disabling patches to modules in the module loader. Hard-coding the
>> function calls ensures that ftrace_module_enable() is run before
>> klp_module_coming() during module load, and that klp_module_going() is
>> run before ftrace_release_mod() during module unload. This way, ftrace
>> and livepatch code is run in the correct order during the module
>> load/unload sequence without dependence on the module notifier call chain.
>>
>> Signed-off-by: Jessica Yu <jeyu@redhat.com>
>> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
>> Acked-by: Rusty Russell <rusty@rustcorp.com.au>
>> ---
>>  include/linux/livepatch.h |  13 ++++
>>  kernel/livepatch/core.c   | 147 ++++++++++++++++++++++------------------------
>>  kernel/module.c           |  10 ++++
>>  3 files changed, 94 insertions(+), 76 deletions(-)
>>
>> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
>> index 780f00c..4fafbae 100644
>> --- a/kernel/livepatch/core.c
>> +++ b/kernel/livepatch/core.c
>> @@ -866,103 +866,108 @@ int klp_register_patch(struct klp_patch *patch)
>>  }
>>  EXPORT_SYMBOL_GPL(klp_register_patch);
>>
>> -static int klp_module_notify_coming(struct klp_patch *patch,
>> -				     struct klp_object *obj)
>> +int klp_module_coming(struct module *mod)
>>  {
>> -	struct module *pmod = patch->mod;
>> -	struct module *mod = obj->mod;
>>  	int ret;
>> +	struct klp_patch *patch;
>> +	struct klp_object *obj;
>>
>> -	ret = klp_init_object_loaded(patch, obj);
>> -	if (ret) {
>> -		pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
>> -			pmod->name, mod->name, ret);
>> -		return ret;
>> -	}
>> +	if (WARN_ON(mod->state != MODULE_STATE_COMING))
>> +		return -EINVAL;
>>
>> -	if (patch->state == KLP_DISABLED)
>> -		return 0;
>> +	mutex_lock(&klp_mutex);
>> +	/*
>> +	 * Each module has to know that klp_module_coming()
>> +	 * has been called. We never know what module will
>> +	 * get patched by a new patch.
>> +	 */
>> +	mod->klp_alive = true;
>>
>> -	pr_notice("applying patch '%s' to loading module '%s'\n",
>> -		  pmod->name, mod->name);
>> +	list_for_each_entry(patch, &klp_patches, list) {
>> +		klp_for_each_object(patch, obj) {
>> +			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
>> +				continue;
>>
>> -	ret = klp_enable_object(obj);
>> -	if (ret)
>> -		pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
>> -			pmod->name, mod->name, ret);
>> -	return ret;
>> -}
>> +			obj->mod = mod;
>>
>> -static void klp_module_notify_going(struct klp_patch *patch,
>> -				    struct klp_object *obj)
>> -{
>> -	struct module *pmod = patch->mod;
>> -	struct module *mod = obj->mod;
>> +			ret = klp_init_object_loaded(patch, obj);
>> +			if (ret) {
>> +				pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
>> +					patch->mod->name, obj->mod->name, ret);
>> +				goto err;
>> +			}
>>
>> -	if (patch->state == KLP_DISABLED)
>> -		goto disabled;
>> +			if (patch->state == KLP_DISABLED)
>> +				break;
>> +
>> +			pr_notice("applying patch '%s' to loading module '%s'\n",
>> +				  patch->mod->name, obj->mod->name);
>> +
>> +			ret = klp_enable_object(obj);
>> +			if (ret) {
>> +				pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
>> +					patch->mod->name, obj->mod->name, ret);
>> +				goto err;
>> +			}
>> +
>> +			break;
>> +		}
>> +	}
>>
>> -	pr_notice("reverting patch '%s' on unloading module '%s'\n",
>> -		  pmod->name, mod->name);
>> +	mutex_unlock(&klp_mutex);
>>
>> -	klp_disable_object(obj);
>> +	return 0;
>>
>> -disabled:
>> +err:
>> +	/*
>> +	 * If a patch is unsuccessfully applied, return
>> +	 * error to the module loader.
>> +	 */
>> +	pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
>> +		patch->mod->name, obj->mod->name, obj->mod->name);
>
>One more thing. We should add here:
>
>	mod->klp_alive = true;
>
>Otherwise, there is a small race window when a new patch will try to
>patch the module.

Ah, you are right. I think you meant false, though :-) Will fix that.

>>  	klp_free_object_loaded(obj);
>> +	mutex_unlock(&klp_mutex);
>> +
>> +	return ret;
>>  }
>
>With the above fix:
>
>Reviewed-by: Petr Mladek <pmladek@suse.cz>
>
>
>Best Regards,
>Petr

Re: livepatch/module: remove livepatch module notifier

[Petr Mladek]

On Mon 2016-03-14 13:50:09, Jessica Yu wrote:
> +++ Petr Mladek [14/03/16 16:06 +0100]:
> >On Fri 2016-03-11 15:03:48, Jessica Yu wrote:
> >>+err:
> >>+	/*
> >>+	 * If a patch is unsuccessfully applied, return
> >>+	 * error to the module loader.
> >>+	 */
> >>+	pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
> >>+		patch->mod->name, obj->mod->name, obj->mod->name);
> >
> >One more thing. We should add here:
> >
> >	mod->klp_alive = true;
> >
> >Otherwise, there is a small race window when a new patch will try to
> >patch the module.
> 
> Ah, you are right. I think you meant false, though :-) Will fix that.

Yeah, I meant false :-)

Thanks,
Petr

Re: [PATCH v2 2/2] livepatch/module: remove livepatch module notifier

[Josh Poimboeuf]

On Fri, Mar 11, 2016 at 03:03:48PM -0500, Jessica Yu wrote:
> +/* Module can be either COMING or GOING */

IMO this comment doesn't really add anything: the below WARN_ON already
says as much.  Also the location of the comment right above the function
is confusing: someone not familiar with the code might wonder why the
function is called klp_module_going() if the module can be either coming
or going.  So I think the comment can just be removed.

> +void klp_module_going(struct module *mod)
>  {
> -	int ret;
> -	struct module *mod = data;
>  	struct klp_patch *patch;
>  	struct klp_object *obj;
>  
> -	if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
> -		return 0;
> +	if (WARN_ON(mod->state != MODULE_STATE_GOING &&
> +		    mod->state != MODULE_STATE_COMING))
> +		return;

-- 
Josh