Re: [PATCH 2/2] Yama: add PTRACE exception tracking

[Tetsuo Handa]

Kees Cook wrote:
> @@ -41,18 +41,30 @@ static DEFINE_SPINLOCK(ptracer_relations_lock);
>  static int yama_ptracer_add(struct task_struct *tracer,
>  			    struct task_struct *tracee)
>  {
> -	struct ptrace_relation *relation;
> +	int rc = 0;
> +	struct ptrace_relation *entry, *relation = NULL;
>  
> -	relation = kmalloc(sizeof(*relation), GFP_KERNEL);
> -	if (!relation)
> -		return -ENOMEM;
> -	relation->tracer = tracer;
> -	relation->tracee = tracee;
>  	spin_lock(&ptracer_relations_lock);
> -	list_add(&relation->node, &ptracer_relations);
> +	list_for_each_entry(entry, &ptracer_relations, node)
> +		if (entry->tracee == tracee) {
> +			relation = entry;
> +			break;
> +		}
> +	if (!relation) {
> +		relation = kmalloc(sizeof(*relation), GFP_KERNEL);

You can't use GFP_KERNEL here because a spinlock is held.

> +		if (!relation) {
> +			rc = -ENOMEM;
> +			goto unlock_out;
> +		}
> +		relation->tracee = tracee;
> +		list_add(&relation->node, &ptracer_relations);
> +	}
> +	relation->tracer = tracer;
> +
> +unlock_out:
>  	spin_unlock(&ptracer_relations_lock);
>  
> -	return 0;
> +	return rc;
>  }
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