[PATCH] c/r: pin down modules registered to obj-ops

[PATCH] c/r: pin down modules registered to obj-ops

[Oren Laadan]

To ensure that a module does not unload in the middle of a checkpoint
or a restart operation, pin (module_get) all the modules during either
operation.  For that, add a new memeber ->owner in ckpt_obj_ops.

Also add a counter that keeps track of how many module_gets we have
going on, to properly handle new modules that register when an
operation is underway.

This is a proof of concept, applies on top of the patch that introduces
objhash on rc7 (patch 33).

Todo:

- I put the initialization part in init_*_ctx(), but it could be moved
to ckpt_ctx_alloc() which is common to both checkpoint and restart.

- If this is ok, then additional patches should adjust those modules
that indeed register...

Signed-off-by: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>

---
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 2f5af3c..4ed8a8c 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -40,11 +40,13 @@ extern long do_sys_restart(pid_t pid, int fd,
 #define CKPT_CTX_RESTART_BIT		1
 #define CKPT_CTX_SUCCESS_BIT		2
 #define CKPT_CTX_ERROR_BIT		3
+#define CKPT_CTX_PINNED_BIT		4
 
 #define CKPT_CTX_CHECKPOINT	(1 << CKPT_CTX_CHECKPOINT_BIT)
 #define CKPT_CTX_RESTART	(1 << CKPT_CTX_RESTART_BIT)
 #define CKPT_CTX_SUCCESS	(1 << CKPT_CTX_SUCCESS_BIT)
 #define CKPT_CTX_ERROR		(1 << CKPT_CTX_ERROR_BIT)
+#define CKPT_CTX_PINNED		(1 << CKPT_CTX_PINNED_BIT)
 
 /* ckpt_ctx: uflags */
 #define CHECKPOINT_USER_FLAGS		CHECKPOINT_SUBTREE
@@ -107,6 +109,9 @@ static inline int ckpt_get_error(struct ckpt_ctx *ctx)
 extern void restore_notify_error(struct ckpt_ctx *ctx);
 
 /* obj_hash */
+extern int ckpt_obj_module_get(void);
+extern void ckpt_obj_module_put(void);
+
 extern void ckpt_obj_hash_free(struct ckpt_ctx *ctx);
 extern int ckpt_obj_hash_alloc(struct ckpt_ctx *ctx);
 
@@ -284,6 +289,7 @@ extern void _ckpt_msg_complete(struct ckpt_ctx *ctx);
 
 struct ckpt_obj_ops;
 extern int register_checkpoint_obj(const struct ckpt_obj_ops *ops);
+extern void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops);
 
 #else /* CONFIG_CHEKCPOINT */
 
@@ -293,6 +299,10 @@ static inline int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
 	return 0;
 }
 
+static inline void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
+{
+}
+
 #endif /* CONFIG_CHECKPOINT */
 #endif /* __KERNEL__ */
 
diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h
index 912e06a..8035556 100644
--- a/include/linux/checkpoint_types.h
+++ b/include/linux/checkpoint_types.h
@@ -79,6 +79,7 @@ struct ckpt_obj_ops {
 	int (*ref_grab)(void *ptr);
 	int (*checkpoint)(struct ckpt_ctx *ctx, void *ptr);
 	void *(*restore)(struct ckpt_ctx *ctx);
+	struct module *owner;
 };
 
 
diff --git a/kernel/checkpoint/checkpoint.c b/kernel/checkpoint/checkpoint.c
index f451f8f..1a08bfb 100644
--- a/kernel/checkpoint/checkpoint.c
+++ b/kernel/checkpoint/checkpoint.c
@@ -473,6 +473,7 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
 {
 	struct task_struct *task;
 	struct nsproxy *nsproxy;
+	int ret;
 
 	/*
 	 * No need for explicit cleanup here, because if an error
@@ -514,6 +515,12 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
 		return -EINVAL;  /* cleanup by ckpt_ctx_free() */
 	}
 
+	/* pin down modules - cleanup by ckpt_ctx_free() */
+	ret = ckpt_obj_module_get();
+	if (ret < 0)
+		return ret;
+	ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
+
 	return 0;
 }
 
diff --git a/kernel/checkpoint/objhash.c b/kernel/checkpoint/objhash.c
index 1ee06d0..db795e3 100644
--- a/kernel/checkpoint/objhash.c
+++ b/kernel/checkpoint/objhash.c
@@ -45,17 +45,80 @@ static const struct ckpt_obj_ops *ckpt_obj_ops[CKPT_OBJ_MAX] = {
 	[CKPT_OBJ_IGNORE] = &ckpt_obj_ignored_ops,
 };
 
+static int ckpt_obj_pinned_count;
+static DEFINE_SPINLOCK(ckpt_obj_pinned_lock);
+
 int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
 {
+	int ret = -EINVAL;
+	int i;
+
 	if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
 		return -EINVAL;
-	if (ckpt_obj_ops[ops->obj_type] != NULL)
-		return -EINVAL;
-	ckpt_obj_ops[ops->obj_type] = ops;
-	return 0;
+	spin_lock(&ckpt_obj_pinned_lock);
+	if (ckpt_obj_ops[ops->obj_type] == NULL) {
+		if (ops->owner) {
+			for (i = 0; i < ckpt_obj_pinned_count)
+				__module_get(owner->module);
+		}
+		ckpt_obj_ops[ops->obj_type] = ops;
+		ret = 0;
+	}
+	spin_unlock(&ckpt_obj_pinned_lock);
+	return ret;
 }
 EXPORT_SYMBOL(register_checkpoint_obj);
 
+void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
+{
+	if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
+		return;
+	spin_lock(&ckpt_obj_pinned_lock);
+	if (ckpt_obj_ops[ops->obj_type] == ops)
+		ckpt_obj_ops[ops->obj_type] = NULL;
+	spin_unlock(&ckpt_obj_pinned_lock);
+	return ret;
+}
+EXPORT_SYMBOL(unregister_checkpoint_obj);
+
+static void _ckpt_obj_module_put(int last)
+{
+	int i;
+
+	for (i = 0; i < last; i++) {
+		if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
+			continue;
+		module_put(ckpt_obj_ops[i]->owner);
+	}
+}
+void ckpt_obj_module_put(void)
+{
+	spin_lock(&ckpt_obj_pinned_lock);
+	_ckpt_obj_module_put(CKPT_OBJ_MAX);
+	ckpt_obj_pinned_count--;
+	spin_unlock(&ckpt_obj_pinned_lock);
+}
+
+int ckpt_obj_module_get(void)
+{
+	int i, ret = 0;
+
+	spin_lock(&ckpt_obj_pinned_lock);
+	for (i = 0; i < CKPT_OBJ_MAX; i++) {
+		if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
+			continue;
+		ret = try_module_get(ckpt_obj_ops[i]->owner);
+		if (ret < 0)
+			break;
+	}
+	if (ret < 0)
+		_ckpt_obj_module_put(i);
+	else
+		ckpt_obj_pinned_count++;
+	spin_unlock(&ckpt_obj_pinned_lock);
+	return ret;
+}
+
 #define CKPT_OBJ_HASH_NBITS  10
 #define CKPT_OBJ_HASH_TOTAL  (1UL << CKPT_OBJ_HASH_NBITS)
 
diff --git a/kernel/checkpoint/restart.c b/kernel/checkpoint/restart.c
index 437de4f..582e1f1 100644
--- a/kernel/checkpoint/restart.c
+++ b/kernel/checkpoint/restart.c
@@ -1084,6 +1084,12 @@ static int init_restart_ctx(struct ckpt_ctx *ctx, pid_t pid)
 
 	ctx->active_pid = -1;	/* see restore_activate_next, get_active_pid */
 
+	/* pin down modules - cleanup by ckpt_ctx_free() */
+	ret = ckpt_obj_module_get();
+	if (ret < 0)
+		return ret;
+	ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
+
 	return 0;
 }
 
diff --git a/kernel/checkpoint/sys.c b/kernel/checkpoint/sys.c
index 5e84915..e1a1f96 100644
--- a/kernel/checkpoint/sys.c
+++ b/kernel/checkpoint/sys.c
@@ -217,6 +217,10 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx)
 
 	kfree(ctx->pids_arr);
 
+	/* un-pin modules */
+	if (ctx->kflags & CKPT_CTX_PINNED)
+		ckpt_obj_module_put();
+
 	kfree(ctx);
 }

Re: [PATCH] c/r: pin down modules registered to obj-ops

[Serge E. Hallyn]

Quoting Oren Laadan (orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org):
> To ensure that a module does not unload in the middle of a checkpoint
> or a restart operation, pin (module_get) all the modules during either
> operation.  For that, add a new memeber ->owner in ckpt_obj_ops.
> 
> Also add a counter that keeps track of how many module_gets we have
> going on, to properly handle new modules that register when an
> operation is underway.
> 
> This is a proof of concept, applies on top of the patch that introduces
> objhash on rc7 (patch 33).
> 
> Todo:
> 
> - I put the initialization part in init_*_ctx(), but it could be moved
> to ckpt_ctx_alloc() which is common to both checkpoint and restart.
> 
> - If this is ok, then additional patches should adjust those modules
> that indeed register...
> 
> Signed-off-by: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>

Yes this looks good to me

Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

Were you going to stick this into v21 too, or queue that up as
first patch after the patchbomb?

thanks,
-serge

> 
> ---
> diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
> index 2f5af3c..4ed8a8c 100644
> --- a/include/linux/checkpoint.h
> +++ b/include/linux/checkpoint.h
> @@ -40,11 +40,13 @@ extern long do_sys_restart(pid_t pid, int fd,
>  #define CKPT_CTX_RESTART_BIT		1
>  #define CKPT_CTX_SUCCESS_BIT		2
>  #define CKPT_CTX_ERROR_BIT		3
> +#define CKPT_CTX_PINNED_BIT		4
> 
>  #define CKPT_CTX_CHECKPOINT	(1 << CKPT_CTX_CHECKPOINT_BIT)
>  #define CKPT_CTX_RESTART	(1 << CKPT_CTX_RESTART_BIT)
>  #define CKPT_CTX_SUCCESS	(1 << CKPT_CTX_SUCCESS_BIT)
>  #define CKPT_CTX_ERROR		(1 << CKPT_CTX_ERROR_BIT)
> +#define CKPT_CTX_PINNED		(1 << CKPT_CTX_PINNED_BIT)
> 
>  /* ckpt_ctx: uflags */
>  #define CHECKPOINT_USER_FLAGS		CHECKPOINT_SUBTREE
> @@ -107,6 +109,9 @@ static inline int ckpt_get_error(struct ckpt_ctx *ctx)
>  extern void restore_notify_error(struct ckpt_ctx *ctx);
> 
>  /* obj_hash */
> +extern int ckpt_obj_module_get(void);
> +extern void ckpt_obj_module_put(void);
> +
>  extern void ckpt_obj_hash_free(struct ckpt_ctx *ctx);
>  extern int ckpt_obj_hash_alloc(struct ckpt_ctx *ctx);
> 
> @@ -284,6 +289,7 @@ extern void _ckpt_msg_complete(struct ckpt_ctx *ctx);
> 
>  struct ckpt_obj_ops;
>  extern int register_checkpoint_obj(const struct ckpt_obj_ops *ops);
> +extern void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops);
> 
>  #else /* CONFIG_CHEKCPOINT */
> 
> @@ -293,6 +299,10 @@ static inline int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
>  	return 0;
>  }
> 
> +static inline void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
> +{
> +}
> +
>  #endif /* CONFIG_CHECKPOINT */
>  #endif /* __KERNEL__ */
> 
> diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h
> index 912e06a..8035556 100644
> --- a/include/linux/checkpoint_types.h
> +++ b/include/linux/checkpoint_types.h
> @@ -79,6 +79,7 @@ struct ckpt_obj_ops {
>  	int (*ref_grab)(void *ptr);
>  	int (*checkpoint)(struct ckpt_ctx *ctx, void *ptr);
>  	void *(*restore)(struct ckpt_ctx *ctx);
> +	struct module *owner;
>  };
> 
> 
> diff --git a/kernel/checkpoint/checkpoint.c b/kernel/checkpoint/checkpoint.c
> index f451f8f..1a08bfb 100644
> --- a/kernel/checkpoint/checkpoint.c
> +++ b/kernel/checkpoint/checkpoint.c
> @@ -473,6 +473,7 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
>  {
>  	struct task_struct *task;
>  	struct nsproxy *nsproxy;
> +	int ret;
> 
>  	/*
>  	 * No need for explicit cleanup here, because if an error
> @@ -514,6 +515,12 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
>  		return -EINVAL;  /* cleanup by ckpt_ctx_free() */
>  	}
> 
> +	/* pin down modules - cleanup by ckpt_ctx_free() */
> +	ret = ckpt_obj_module_get();
> +	if (ret < 0)
> +		return ret;
> +	ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
> +
>  	return 0;
>  }
> 
> diff --git a/kernel/checkpoint/objhash.c b/kernel/checkpoint/objhash.c
> index 1ee06d0..db795e3 100644
> --- a/kernel/checkpoint/objhash.c
> +++ b/kernel/checkpoint/objhash.c
> @@ -45,17 +45,80 @@ static const struct ckpt_obj_ops *ckpt_obj_ops[CKPT_OBJ_MAX] = {
>  	[CKPT_OBJ_IGNORE] = &ckpt_obj_ignored_ops,
>  };
> 
> +static int ckpt_obj_pinned_count;
> +static DEFINE_SPINLOCK(ckpt_obj_pinned_lock);
> +
>  int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
>  {
> +	int ret = -EINVAL;
> +	int i;
> +
>  	if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
>  		return -EINVAL;
> -	if (ckpt_obj_ops[ops->obj_type] != NULL)
> -		return -EINVAL;
> -	ckpt_obj_ops[ops->obj_type] = ops;
> -	return 0;
> +	spin_lock(&ckpt_obj_pinned_lock);
> +	if (ckpt_obj_ops[ops->obj_type] == NULL) {
> +		if (ops->owner) {
> +			for (i = 0; i < ckpt_obj_pinned_count)
> +				__module_get(owner->module);
> +		}
> +		ckpt_obj_ops[ops->obj_type] = ops;
> +		ret = 0;
> +	}
> +	spin_unlock(&ckpt_obj_pinned_lock);
> +	return ret;
>  }
>  EXPORT_SYMBOL(register_checkpoint_obj);
> 
> +void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
> +{
> +	if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
> +		return;
> +	spin_lock(&ckpt_obj_pinned_lock);
> +	if (ckpt_obj_ops[ops->obj_type] == ops)
> +		ckpt_obj_ops[ops->obj_type] = NULL;
> +	spin_unlock(&ckpt_obj_pinned_lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL(unregister_checkpoint_obj);
> +
> +static void _ckpt_obj_module_put(int last)
> +{
> +	int i;
> +
> +	for (i = 0; i < last; i++) {
> +		if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
> +			continue;
> +		module_put(ckpt_obj_ops[i]->owner);
> +	}
> +}
> +void ckpt_obj_module_put(void)
> +{
> +	spin_lock(&ckpt_obj_pinned_lock);
> +	_ckpt_obj_module_put(CKPT_OBJ_MAX);
> +	ckpt_obj_pinned_count--;
> +	spin_unlock(&ckpt_obj_pinned_lock);
> +}
> +
> +int ckpt_obj_module_get(void)
> +{
> +	int i, ret = 0;
> +
> +	spin_lock(&ckpt_obj_pinned_lock);
> +	for (i = 0; i < CKPT_OBJ_MAX; i++) {
> +		if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
> +			continue;
> +		ret = try_module_get(ckpt_obj_ops[i]->owner);
> +		if (ret < 0)
> +			break;
> +	}
> +	if (ret < 0)
> +		_ckpt_obj_module_put(i);
> +	else
> +		ckpt_obj_pinned_count++;
> +	spin_unlock(&ckpt_obj_pinned_lock);
> +	return ret;
> +}
> +
>  #define CKPT_OBJ_HASH_NBITS  10
>  #define CKPT_OBJ_HASH_TOTAL  (1UL << CKPT_OBJ_HASH_NBITS)
> 
> diff --git a/kernel/checkpoint/restart.c b/kernel/checkpoint/restart.c
> index 437de4f..582e1f1 100644
> --- a/kernel/checkpoint/restart.c
> +++ b/kernel/checkpoint/restart.c
> @@ -1084,6 +1084,12 @@ static int init_restart_ctx(struct ckpt_ctx *ctx, pid_t pid)
> 
>  	ctx->active_pid = -1;	/* see restore_activate_next, get_active_pid */
> 
> +	/* pin down modules - cleanup by ckpt_ctx_free() */
> +	ret = ckpt_obj_module_get();
> +	if (ret < 0)
> +		return ret;
> +	ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
> +
>  	return 0;
>  }
> 
> diff --git a/kernel/checkpoint/sys.c b/kernel/checkpoint/sys.c
> index 5e84915..e1a1f96 100644
> --- a/kernel/checkpoint/sys.c
> +++ b/kernel/checkpoint/sys.c
> @@ -217,6 +217,10 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx)
> 
>  	kfree(ctx->pids_arr);
> 
> +	/* un-pin modules */
> +	if (ctx->kflags & CKPT_CTX_PINNED)
> +		ckpt_obj_module_put();
> +
>  	kfree(ctx);
>  }

Re: [PATCH] c/r: pin down modules registered to obj-ops

[Oren Laadan]

I don't feel comfortable with posting a version that we know
can crash a kernel, and even less so if we say that's it's broken...
So I prefer it inside.

Oren

Serge E. Hallyn wrote:
> Quoting Oren Laadan (orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org):
>> To ensure that a module does not unload in the middle of a checkpoint
>> or a restart operation, pin (module_get) all the modules during either
>> operation.  For that, add a new memeber ->owner in ckpt_obj_ops.
>>
>> Also add a counter that keeps track of how many module_gets we have
>> going on, to properly handle new modules that register when an
>> operation is underway.
>>
>> This is a proof of concept, applies on top of the patch that introduces
>> objhash on rc7 (patch 33).
>>
>> Todo:
>>
>> - I put the initialization part in init_*_ctx(), but it could be moved
>> to ckpt_ctx_alloc() which is common to both checkpoint and restart.
>>
>> - If this is ok, then additional patches should adjust those modules
>> that indeed register...
>>
>> Signed-off-by: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
> 
> Yes this looks good to me
> 
> Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> 
> Were you going to stick this into v21 too, or queue that up as
> first patch after the patchbomb?
> 
> thanks,
> -serge
> 
>> ---
>> diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
>> index 2f5af3c..4ed8a8c 100644
>> --- a/include/linux/checkpoint.h
>> +++ b/include/linux/checkpoint.h
>> @@ -40,11 +40,13 @@ extern long do_sys_restart(pid_t pid, int fd,
>>  #define CKPT_CTX_RESTART_BIT		1
>>  #define CKPT_CTX_SUCCESS_BIT		2
>>  #define CKPT_CTX_ERROR_BIT		3
>> +#define CKPT_CTX_PINNED_BIT		4
>>
>>  #define CKPT_CTX_CHECKPOINT	(1 << CKPT_CTX_CHECKPOINT_BIT)
>>  #define CKPT_CTX_RESTART	(1 << CKPT_CTX_RESTART_BIT)
>>  #define CKPT_CTX_SUCCESS	(1 << CKPT_CTX_SUCCESS_BIT)
>>  #define CKPT_CTX_ERROR		(1 << CKPT_CTX_ERROR_BIT)
>> +#define CKPT_CTX_PINNED		(1 << CKPT_CTX_PINNED_BIT)
>>
>>  /* ckpt_ctx: uflags */
>>  #define CHECKPOINT_USER_FLAGS		CHECKPOINT_SUBTREE
>> @@ -107,6 +109,9 @@ static inline int ckpt_get_error(struct ckpt_ctx *ctx)
>>  extern void restore_notify_error(struct ckpt_ctx *ctx);
>>
>>  /* obj_hash */
>> +extern int ckpt_obj_module_get(void);
>> +extern void ckpt_obj_module_put(void);
>> +
>>  extern void ckpt_obj_hash_free(struct ckpt_ctx *ctx);
>>  extern int ckpt_obj_hash_alloc(struct ckpt_ctx *ctx);
>>
>> @@ -284,6 +289,7 @@ extern void _ckpt_msg_complete(struct ckpt_ctx *ctx);
>>
>>  struct ckpt_obj_ops;
>>  extern int register_checkpoint_obj(const struct ckpt_obj_ops *ops);
>> +extern void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops);
>>
>>  #else /* CONFIG_CHEKCPOINT */
>>
>> @@ -293,6 +299,10 @@ static inline int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
>>  	return 0;
>>  }
>>
>> +static inline void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
>> +{
>> +}
>> +
>>  #endif /* CONFIG_CHECKPOINT */
>>  #endif /* __KERNEL__ */
>>
>> diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h
>> index 912e06a..8035556 100644
>> --- a/include/linux/checkpoint_types.h
>> +++ b/include/linux/checkpoint_types.h
>> @@ -79,6 +79,7 @@ struct ckpt_obj_ops {
>>  	int (*ref_grab)(void *ptr);
>>  	int (*checkpoint)(struct ckpt_ctx *ctx, void *ptr);
>>  	void *(*restore)(struct ckpt_ctx *ctx);
>> +	struct module *owner;
>>  };
>>
>>
>> diff --git a/kernel/checkpoint/checkpoint.c b/kernel/checkpoint/checkpoint.c
>> index f451f8f..1a08bfb 100644
>> --- a/kernel/checkpoint/checkpoint.c
>> +++ b/kernel/checkpoint/checkpoint.c
>> @@ -473,6 +473,7 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
>>  {
>>  	struct task_struct *task;
>>  	struct nsproxy *nsproxy;
>> +	int ret;
>>
>>  	/*
>>  	 * No need for explicit cleanup here, because if an error
>> @@ -514,6 +515,12 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
>>  		return -EINVAL;  /* cleanup by ckpt_ctx_free() */
>>  	}
>>
>> +	/* pin down modules - cleanup by ckpt_ctx_free() */
>> +	ret = ckpt_obj_module_get();
>> +	if (ret < 0)
>> +		return ret;
>> +	ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
>> +
>>  	return 0;
>>  }
>>
>> diff --git a/kernel/checkpoint/objhash.c b/kernel/checkpoint/objhash.c
>> index 1ee06d0..db795e3 100644
>> --- a/kernel/checkpoint/objhash.c
>> +++ b/kernel/checkpoint/objhash.c
>> @@ -45,17 +45,80 @@ static const struct ckpt_obj_ops *ckpt_obj_ops[CKPT_OBJ_MAX] = {
>>  	[CKPT_OBJ_IGNORE] = &ckpt_obj_ignored_ops,
>>  };
>>
>> +static int ckpt_obj_pinned_count;
>> +static DEFINE_SPINLOCK(ckpt_obj_pinned_lock);
>> +
>>  int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
>>  {
>> +	int ret = -EINVAL;
>> +	int i;
>> +
>>  	if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
>>  		return -EINVAL;
>> -	if (ckpt_obj_ops[ops->obj_type] != NULL)
>> -		return -EINVAL;
>> -	ckpt_obj_ops[ops->obj_type] = ops;
>> -	return 0;
>> +	spin_lock(&ckpt_obj_pinned_lock);
>> +	if (ckpt_obj_ops[ops->obj_type] == NULL) {
>> +		if (ops->owner) {
>> +			for (i = 0; i < ckpt_obj_pinned_count)
>> +				__module_get(owner->module);
>> +		}
>> +		ckpt_obj_ops[ops->obj_type] = ops;
>> +		ret = 0;
>> +	}
>> +	spin_unlock(&ckpt_obj_pinned_lock);
>> +	return ret;
>>  }
>>  EXPORT_SYMBOL(register_checkpoint_obj);
>>
>> +void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
>> +{
>> +	if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
>> +		return;
>> +	spin_lock(&ckpt_obj_pinned_lock);
>> +	if (ckpt_obj_ops[ops->obj_type] == ops)
>> +		ckpt_obj_ops[ops->obj_type] = NULL;
>> +	spin_unlock(&ckpt_obj_pinned_lock);
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL(unregister_checkpoint_obj);
>> +
>> +static void _ckpt_obj_module_put(int last)
>> +{
>> +	int i;
>> +
>> +	for (i = 0; i < last; i++) {
>> +		if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
>> +			continue;
>> +		module_put(ckpt_obj_ops[i]->owner);
>> +	}
>> +}
>> +void ckpt_obj_module_put(void)
>> +{
>> +	spin_lock(&ckpt_obj_pinned_lock);
>> +	_ckpt_obj_module_put(CKPT_OBJ_MAX);
>> +	ckpt_obj_pinned_count--;
>> +	spin_unlock(&ckpt_obj_pinned_lock);
>> +}
>> +
>> +int ckpt_obj_module_get(void)
>> +{
>> +	int i, ret = 0;
>> +
>> +	spin_lock(&ckpt_obj_pinned_lock);
>> +	for (i = 0; i < CKPT_OBJ_MAX; i++) {
>> +		if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
>> +			continue;
>> +		ret = try_module_get(ckpt_obj_ops[i]->owner);
>> +		if (ret < 0)
>> +			break;
>> +	}
>> +	if (ret < 0)
>> +		_ckpt_obj_module_put(i);
>> +	else
>> +		ckpt_obj_pinned_count++;
>> +	spin_unlock(&ckpt_obj_pinned_lock);
>> +	return ret;
>> +}
>> +
>>  #define CKPT_OBJ_HASH_NBITS  10
>>  #define CKPT_OBJ_HASH_TOTAL  (1UL << CKPT_OBJ_HASH_NBITS)
>>
>> diff --git a/kernel/checkpoint/restart.c b/kernel/checkpoint/restart.c
>> index 437de4f..582e1f1 100644
>> --- a/kernel/checkpoint/restart.c
>> +++ b/kernel/checkpoint/restart.c
>> @@ -1084,6 +1084,12 @@ static int init_restart_ctx(struct ckpt_ctx *ctx, pid_t pid)
>>
>>  	ctx->active_pid = -1;	/* see restore_activate_next, get_active_pid */
>>
>> +	/* pin down modules - cleanup by ckpt_ctx_free() */
>> +	ret = ckpt_obj_module_get();
>> +	if (ret < 0)
>> +		return ret;
>> +	ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
>> +
>>  	return 0;
>>  }
>>
>> diff --git a/kernel/checkpoint/sys.c b/kernel/checkpoint/sys.c
>> index 5e84915..e1a1f96 100644
>> --- a/kernel/checkpoint/sys.c
>> +++ b/kernel/checkpoint/sys.c
>> @@ -217,6 +217,10 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx)
>>
>>  	kfree(ctx->pids_arr);
>>
>> +	/* un-pin modules */
>> +	if (ctx->kflags & CKPT_CTX_PINNED)
>> +		ckpt_obj_module_put();
>> +
>>  	kfree(ctx);
>>  }
> 

Re: [PATCH] c/r: pin down modules registered to obj-ops

[Serge E. Hallyn]

How can it crash kernels?  At the moment every ckpt_ops that is
registered is done so from files which are not parts of modules.

Quoting Oren Laadan (orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org):
> 
> I don't feel comfortable with posting a version that we know
> can crash a kernel, and even less so if we say that's it's broken...
> So I prefer it inside.
> 
> Oren
> 
> Serge E. Hallyn wrote:
> > Quoting Oren Laadan (orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org):
> >> To ensure that a module does not unload in the middle of a checkpoint
> >> or a restart operation, pin (module_get) all the modules during either
> >> operation.  For that, add a new memeber ->owner in ckpt_obj_ops.
> >>
> >> Also add a counter that keeps track of how many module_gets we have
> >> going on, to properly handle new modules that register when an
> >> operation is underway.
> >>
> >> This is a proof of concept, applies on top of the patch that introduces
> >> objhash on rc7 (patch 33).
> >>
> >> Todo:
> >>
> >> - I put the initialization part in init_*_ctx(), but it could be moved
> >> to ckpt_ctx_alloc() which is common to both checkpoint and restart.
> >>
> >> - If this is ok, then additional patches should adjust those modules
> >> that indeed register...
> >>
> >> Signed-off-by: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
> > 
> > Yes this looks good to me
> > 
> > Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> > 
> > Were you going to stick this into v21 too, or queue that up as
> > first patch after the patchbomb?
> > 
> > thanks,
> > -serge
> > 
> >> ---
> >> diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
> >> index 2f5af3c..4ed8a8c 100644
> >> --- a/include/linux/checkpoint.h
> >> +++ b/include/linux/checkpoint.h
> >> @@ -40,11 +40,13 @@ extern long do_sys_restart(pid_t pid, int fd,
> >>  #define CKPT_CTX_RESTART_BIT		1
> >>  #define CKPT_CTX_SUCCESS_BIT		2
> >>  #define CKPT_CTX_ERROR_BIT		3
> >> +#define CKPT_CTX_PINNED_BIT		4
> >>
> >>  #define CKPT_CTX_CHECKPOINT	(1 << CKPT_CTX_CHECKPOINT_BIT)
> >>  #define CKPT_CTX_RESTART	(1 << CKPT_CTX_RESTART_BIT)
> >>  #define CKPT_CTX_SUCCESS	(1 << CKPT_CTX_SUCCESS_BIT)
> >>  #define CKPT_CTX_ERROR		(1 << CKPT_CTX_ERROR_BIT)
> >> +#define CKPT_CTX_PINNED		(1 << CKPT_CTX_PINNED_BIT)
> >>
> >>  /* ckpt_ctx: uflags */
> >>  #define CHECKPOINT_USER_FLAGS		CHECKPOINT_SUBTREE
> >> @@ -107,6 +109,9 @@ static inline int ckpt_get_error(struct ckpt_ctx *ctx)
> >>  extern void restore_notify_error(struct ckpt_ctx *ctx);
> >>
> >>  /* obj_hash */
> >> +extern int ckpt_obj_module_get(void);
> >> +extern void ckpt_obj_module_put(void);
> >> +
> >>  extern void ckpt_obj_hash_free(struct ckpt_ctx *ctx);
> >>  extern int ckpt_obj_hash_alloc(struct ckpt_ctx *ctx);
> >>
> >> @@ -284,6 +289,7 @@ extern void _ckpt_msg_complete(struct ckpt_ctx *ctx);
> >>
> >>  struct ckpt_obj_ops;
> >>  extern int register_checkpoint_obj(const struct ckpt_obj_ops *ops);
> >> +extern void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops);
> >>
> >>  #else /* CONFIG_CHEKCPOINT */
> >>
> >> @@ -293,6 +299,10 @@ static inline int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
> >>  	return 0;
> >>  }
> >>
> >> +static inline void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
> >> +{
> >> +}
> >> +
> >>  #endif /* CONFIG_CHECKPOINT */
> >>  #endif /* __KERNEL__ */
> >>
> >> diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h
> >> index 912e06a..8035556 100644
> >> --- a/include/linux/checkpoint_types.h
> >> +++ b/include/linux/checkpoint_types.h
> >> @@ -79,6 +79,7 @@ struct ckpt_obj_ops {
> >>  	int (*ref_grab)(void *ptr);
> >>  	int (*checkpoint)(struct ckpt_ctx *ctx, void *ptr);
> >>  	void *(*restore)(struct ckpt_ctx *ctx);
> >> +	struct module *owner;
> >>  };
> >>
> >>
> >> diff --git a/kernel/checkpoint/checkpoint.c b/kernel/checkpoint/checkpoint.c
> >> index f451f8f..1a08bfb 100644
> >> --- a/kernel/checkpoint/checkpoint.c
> >> +++ b/kernel/checkpoint/checkpoint.c
> >> @@ -473,6 +473,7 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
> >>  {
> >>  	struct task_struct *task;
> >>  	struct nsproxy *nsproxy;
> >> +	int ret;
> >>
> >>  	/*
> >>  	 * No need for explicit cleanup here, because if an error
> >> @@ -514,6 +515,12 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
> >>  		return -EINVAL;  /* cleanup by ckpt_ctx_free() */
> >>  	}
> >>
> >> +	/* pin down modules - cleanup by ckpt_ctx_free() */
> >> +	ret = ckpt_obj_module_get();
> >> +	if (ret < 0)
> >> +		return ret;
> >> +	ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
> >> +
> >>  	return 0;
> >>  }
> >>
> >> diff --git a/kernel/checkpoint/objhash.c b/kernel/checkpoint/objhash.c
> >> index 1ee06d0..db795e3 100644
> >> --- a/kernel/checkpoint/objhash.c
> >> +++ b/kernel/checkpoint/objhash.c
> >> @@ -45,17 +45,80 @@ static const struct ckpt_obj_ops *ckpt_obj_ops[CKPT_OBJ_MAX] = {
> >>  	[CKPT_OBJ_IGNORE] = &ckpt_obj_ignored_ops,
> >>  };
> >>
> >> +static int ckpt_obj_pinned_count;
> >> +static DEFINE_SPINLOCK(ckpt_obj_pinned_lock);
> >> +
> >>  int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
> >>  {
> >> +	int ret = -EINVAL;
> >> +	int i;
> >> +
> >>  	if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
> >>  		return -EINVAL;
> >> -	if (ckpt_obj_ops[ops->obj_type] != NULL)
> >> -		return -EINVAL;
> >> -	ckpt_obj_ops[ops->obj_type] = ops;
> >> -	return 0;
> >> +	spin_lock(&ckpt_obj_pinned_lock);
> >> +	if (ckpt_obj_ops[ops->obj_type] == NULL) {
> >> +		if (ops->owner) {
> >> +			for (i = 0; i < ckpt_obj_pinned_count)
> >> +				__module_get(owner->module);
> >> +		}
> >> +		ckpt_obj_ops[ops->obj_type] = ops;
> >> +		ret = 0;
> >> +	}
> >> +	spin_unlock(&ckpt_obj_pinned_lock);
> >> +	return ret;
> >>  }
> >>  EXPORT_SYMBOL(register_checkpoint_obj);
> >>
> >> +void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
> >> +{
> >> +	if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
> >> +		return;
> >> +	spin_lock(&ckpt_obj_pinned_lock);
> >> +	if (ckpt_obj_ops[ops->obj_type] == ops)
> >> +		ckpt_obj_ops[ops->obj_type] = NULL;
> >> +	spin_unlock(&ckpt_obj_pinned_lock);
> >> +	return ret;
> >> +}
> >> +EXPORT_SYMBOL(unregister_checkpoint_obj);
> >> +
> >> +static void _ckpt_obj_module_put(int last)
> >> +{
> >> +	int i;
> >> +
> >> +	for (i = 0; i < last; i++) {
> >> +		if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
> >> +			continue;
> >> +		module_put(ckpt_obj_ops[i]->owner);
> >> +	}
> >> +}
> >> +void ckpt_obj_module_put(void)
> >> +{
> >> +	spin_lock(&ckpt_obj_pinned_lock);
> >> +	_ckpt_obj_module_put(CKPT_OBJ_MAX);
> >> +	ckpt_obj_pinned_count--;
> >> +	spin_unlock(&ckpt_obj_pinned_lock);
> >> +}
> >> +
> >> +int ckpt_obj_module_get(void)
> >> +{
> >> +	int i, ret = 0;
> >> +
> >> +	spin_lock(&ckpt_obj_pinned_lock);
> >> +	for (i = 0; i < CKPT_OBJ_MAX; i++) {
> >> +		if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
> >> +			continue;
> >> +		ret = try_module_get(ckpt_obj_ops[i]->owner);
> >> +		if (ret < 0)
> >> +			break;
> >> +	}
> >> +	if (ret < 0)
> >> +		_ckpt_obj_module_put(i);
> >> +	else
> >> +		ckpt_obj_pinned_count++;
> >> +	spin_unlock(&ckpt_obj_pinned_lock);
> >> +	return ret;
> >> +}
> >> +
> >>  #define CKPT_OBJ_HASH_NBITS  10
> >>  #define CKPT_OBJ_HASH_TOTAL  (1UL << CKPT_OBJ_HASH_NBITS)
> >>
> >> diff --git a/kernel/checkpoint/restart.c b/kernel/checkpoint/restart.c
> >> index 437de4f..582e1f1 100644
> >> --- a/kernel/checkpoint/restart.c
> >> +++ b/kernel/checkpoint/restart.c
> >> @@ -1084,6 +1084,12 @@ static int init_restart_ctx(struct ckpt_ctx *ctx, pid_t pid)
> >>
> >>  	ctx->active_pid = -1;	/* see restore_activate_next, get_active_pid */
> >>
> >> +	/* pin down modules - cleanup by ckpt_ctx_free() */
> >> +	ret = ckpt_obj_module_get();
> >> +	if (ret < 0)
> >> +		return ret;
> >> +	ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
> >> +
> >>  	return 0;
> >>  }
> >>
> >> diff --git a/kernel/checkpoint/sys.c b/kernel/checkpoint/sys.c
> >> index 5e84915..e1a1f96 100644
> >> --- a/kernel/checkpoint/sys.c
> >> +++ b/kernel/checkpoint/sys.c
> >> @@ -217,6 +217,10 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx)
> >>
> >>  	kfree(ctx->pids_arr);
> >>
> >> +	/* un-pin modules */
> >> +	if (ctx->kflags & CKPT_CTX_PINNED)
> >> +		ckpt_obj_module_put();
> >> +
> >>  	kfree(ctx);
> >>  }
> > 
> _______________________________________________
> Containers mailing list
> Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> https://lists.linux-foundation.org/mailman/listinfo/containers

Re: [PATCH] c/r: pin down modules registered to obj-ops

[Oren Laadan]

Serge E. Hallyn wrote:
> How can it crash kernels?  At the moment every ckpt_ops that is
> registered is done so from files which are not parts of modules.

... that's a good point.
Ok then - the patch will wait.

Oren.

> 
> Quoting Oren Laadan (orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org):
>> I don't feel comfortable with posting a version that we know
>> can crash a kernel, and even less so if we say that's it's broken...
>> So I prefer it inside.