[PATCH] drm/amdkfd: explicitly create/destroy queue attributes under /sys

[Felix Kuehling]

Am 2021-12-09 um 2:49 a.m. schrieb Xiaogang.Chen:
> From: Xiaogang Chen <xiaogang.chen at amd.com>
>
> When application is about finish it destroys queues it has created by
> an ioctl. Driver deletes queue entry(/sys/class/kfd/kfd/proc/pid/queues/queueid/)
> which is directory including this queue all attributes. Low level kernel
> code deletes all attributes under this directory. The lock from kernel is
> on queue entry, not its attributes. At meantime another user space application
> can read the attributes. There is possibility that the application can
> hold/read the attributes while kernel is deleting the queue entry, cause
> the application have invalid memory access, then killed by kernel.
>
> Driver changes: explicitly create/destroy each attribute for each queue,
> let kernel put lock on each attribute too.

Is this working around a bug in kobject_del? Shouldn't that code take
care of the necessary locking itself?

Regards,
  Felix


>
> Signed-off-by: Xiaogang Chen <xiaogang.chen at amd.com>
> ---
>  drivers/gpu/drm/amd/amdkfd/kfd_priv.h    |  3 +++
>  drivers/gpu/drm/amd/amdkfd/kfd_process.c | 33 +++++++-----------------
>  2 files changed, 13 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
> index 0c3f911e3bf4..045da300749e 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
> @@ -546,6 +546,9 @@ struct queue {
>  
>  	/* procfs */
>  	struct kobject kobj;
> +	struct attribute attr_guid;
> +	struct attribute attr_size;
> +	struct attribute attr_type;
>  };
>  
>  enum KFD_MQD_TYPE {
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> index 9158f9754a24..04a5638f9196 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> @@ -73,6 +73,8 @@ static void evict_process_worker(struct work_struct *work);
>  static void restore_process_worker(struct work_struct *work);
>  
>  static void kfd_process_device_destroy_cwsr_dgpu(struct kfd_process_device *pdd);
> +static void kfd_sysfs_create_file(struct kobject *kobj, struct attribute *attr,
> +				char *name);
>  
>  struct kfd_procfs_tree {
>  	struct kobject *kobj;
> @@ -441,35 +443,12 @@ static ssize_t kfd_sysfs_counters_show(struct kobject *kobj,
>  	return 0;
>  }
>  
> -static struct attribute attr_queue_size = {
> -	.name = "size",
> -	.mode = KFD_SYSFS_FILE_MODE
> -};
> -
> -static struct attribute attr_queue_type = {
> -	.name = "type",
> -	.mode = KFD_SYSFS_FILE_MODE
> -};
> -
> -static struct attribute attr_queue_gpuid = {
> -	.name = "gpuid",
> -	.mode = KFD_SYSFS_FILE_MODE
> -};
> -
> -static struct attribute *procfs_queue_attrs[] = {
> -	&attr_queue_size,
> -	&attr_queue_type,
> -	&attr_queue_gpuid,
> -	NULL
> -};
> -
>  static const struct sysfs_ops procfs_queue_ops = {
>  	.show = kfd_procfs_queue_show,
>  };
>  
>  static struct kobj_type procfs_queue_type = {
>  	.sysfs_ops = &procfs_queue_ops,
> -	.default_attrs = procfs_queue_attrs,
>  };
>  
>  static const struct sysfs_ops procfs_stats_ops = {
> @@ -511,6 +490,10 @@ int kfd_procfs_add_queue(struct queue *q)
>  		return ret;
>  	}
>  
> +	kfd_sysfs_create_file(&q->kobj, &q->attr_guid, "guid");
> +	kfd_sysfs_create_file(&q->kobj, &q->attr_size, "size");
> +	kfd_sysfs_create_file(&q->kobj, &q->attr_type, "type");
> +
>  	return 0;
>  }
>  
> @@ -655,6 +638,10 @@ void kfd_procfs_del_queue(struct queue *q)
>  	if (!q)
>  		return;
>  
> +	sysfs_remove_file(&q->kobj, &q->attr_guid);
> +	sysfs_remove_file(&q->kobj, &q->attr_size);
> +	sysfs_remove_file(&q->kobj, &q->attr_type);
> +
>  	kobject_del(&q->kobj);
>  	kobject_put(&q->kobj);
>  }