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Date:   Wed, 12 Apr 2023 10:22:57 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     Jaewon Kim <jaewon31.kim@samsung.com>
Cc:     jstultz@google.com, tjmercier@google.com, sumit.semwal@linaro.org,
        daniel.vetter@ffwll.ch, akpm@linux-foundation.org,
        hannes@cmpxchg.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com
Subject: Re: [PATCH v3] dma-buf/heaps: system_heap: avoid too much allocation
Message-ID: <ZDZqYTSHBNGLq0zI@dhcp22.suse.cz>
References: <CGME20230410073304epcas1p4cf3079b096994d69472b7801bd530bc7@epcas1p4.samsung.com>
 <20230410073228.23043-1-jaewon31.kim@samsung.com>
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Sorry for being late. I know there was some pre-existing discussion
around that but I didn't have time to participate.

On Mon 10-04-23 16:32:28, Jaewon Kim wrote:
> @@ -350,6 +350,9 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
>  	struct page *page, *tmp_page;
>  	int i, ret = -ENOMEM;
>  
> +	if (len / PAGE_SIZE > totalram_pages())
> +		return ERR_PTR(-ENOMEM);
> +

This is an antipattern imho. Check 7661809d493b ("mm: don't allow
oversized kvmalloc() calls") how kvmalloc has dealt with a similar
issue. totalram_pages doesn't really tell you anything about incorrect
users. You might be on a low memory system where the request size is
sane normally, it just doesn't fit into memory on that particular
machine.


>  	buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
>  	if (!buffer)
>  		return ERR_PTR(-ENOMEM);
> -- 
> 2.17.1

-- 
Michal Hocko
SUSE Labs