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Date: Tue, 9 Jun 2026 18:13:46 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Samuel Moelius <sam.moelius@trailofbits.com>
Cc: linux-kernel@vger.kernel.org (open list:LIBRARY CODE)
Subject: Re: [PATCH] lib: interval_tree_test: validate benchmark parameters
Message-Id: <20260609181346.dc7a09e0b23b8bd6847d6454@linux-foundation.org>
In-Reply-To: <20260609005446.1241288.1525a5964698.interval-tree-test-small-max-endpoint-div0@trailofbits.com>
References: <20260609005446.1241288.1525a5964698.interval-tree-test-small-max-endpoint-div0@trailofbits.com>
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On Tue,  9 Jun 2026 00:54:47 +0000 Samuel Moelius <sam.moelius@trailofbits.com> wrote:

> The interval tree runtime test accepts module parameters that are later
> used as divisors while generating randomized intervals and while
> reporting average timings. For example, max_endpoint=1 makes the
> generated interval end value zero and the next modulo operation divides
> by that zero value.
> 
> Reject non-positive counts and require max_endpoint to provide at least
> one non-zero generated endpoint before the test allocates state or
> starts the benchmark.

That makes sense, thanks.

> --- a/lib/interval_tree_test.c
> +++ b/lib/interval_tree_test.c
> @@ -311,6 +311,27 @@ static inline int span_iteration_check(void) {return 0; }
>  
>  static int interval_tree_test_init(void)
>  {
> +	if (nnodes <= 0) {
> +		pr_warn("nnodes must be positive\n");
> +		return -EINVAL;
> +	}
> +	if (nsearches <= 0) {
> +		pr_warn("nsearches must be positive\n");
> +		return -EINVAL;
> +	}
> +	if (perf_loops <= 0) {
> +		pr_warn("perf_loops must be positive\n");
> +		return -EINVAL;
> +	}
> +	if (search_loops <= 0) {
> +		pr_warn("search_loops must be positive\n");
> +		return -EINVAL;
> +	}
> +	if (max_endpoint < 2) {
> +		pr_warn("max_endpoint must be at least 2\n");
> +		return -EINVAL;
> +	}
> +
>  	nodes = kmalloc_objs(struct interval_tree_node, nnodes);
>  	if (!nodes)
>  		return -ENOMEM;

Perhaps this can be done within the __param macro:

#define __param(type, name, init, msg)					\
	static type name = init;					\
	module_param(name, type, 0444);					\
	if (name <= 0) {						\
		pr_warn(__stringify(name) " must be positive\n");	\
		name = init;						\
	}								\
	MODULE_PARM_DESC(name, msg);

I'll add your patch as-is.  If you prefer the above approach, please send
along a replacement patch.