linux-kernel - Re: [PATCH v7 5/7] mm, kasan: Stackdepot implementation. Enable stackdepot for SLAB

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Message-ID: <20160411074452.GC26116@js1304-P5Q-DELUXE>
Date:	Mon, 11 Apr 2016 16:44:52 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Alexander Potapenko <glider@...gle.com>
Cc:	adech.fo@...il.com, cl@...ux.com, dvyukov@...gle.com,
	akpm@...ux-foundation.org, ryabinin.a.a@...il.com,
	rostedt@...dmis.org, kcc@...gle.com, kasan-dev@...glegroups.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v7 5/7] mm, kasan: Stackdepot implementation. Enable
 stackdepot for SLAB

On Mon, Mar 14, 2016 at 11:43:43AM +0100, Alexander Potapenko wrote:
> +depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
> +				    gfp_t alloc_flags)
> +{
> +	u32 hash;
> +	depot_stack_handle_t retval = 0;
> +	struct stack_record *found = NULL, **bucket;
> +	unsigned long flags;
> +	struct page *page = NULL;
> +	void *prealloc = NULL;
> +	bool *rec;
> +
> +	if (unlikely(trace->nr_entries == 0))
> +		goto fast_exit;
> +
> +	rec = this_cpu_ptr(&depot_recursion);
> +	/* Don't store the stack if we've been called recursively. */
> +	if (unlikely(*rec))
> +		goto fast_exit;
> +	*rec = true;
> +
> +	hash = hash_stack(trace->entries, trace->nr_entries);
> +	/* Bad luck, we won't store this stack. */
> +	if (hash == 0)
> +		goto exit;

Hello,

why is hash == 0 skipped?

Thanks.