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From: Uladzislau Rezki <urezki@gmail.com>
Date: Mon, 22 Apr 2024 11:40:56 +0200
To: hailong.liu@oppo.com
Cc: akpm@linux-foundation.org, urezki@gmail.com, hch@infradead.org,
	lstoakes@gmail.com, 21cnbao@gmail.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2] mm/vmalloc: fix return value of vb_alloc if size
 is 0.
Message-ID: <ZiYwqBQCi-udlfLz@pc636>
References: <20240419101643.11534-1-hailong.liu@oppo.com>
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In-Reply-To: <20240419101643.11534-1-hailong.liu@oppo.com>

On Fri, Apr 19, 2024 at 06:16:43PM +0800, hailong.liu@oppo.com wrote:
> From: "Hailong.Liu" <hailong.liu@oppo.com>
> 
> vm_map_ram check return value of vb_alloc by IS_ERR. if
> vm_map_ram(page, 0, 0) , vb_alloc(0, GFP_KERNEL) would return NULL
> which cause kernel panic by vmap_pages_range_noflush。fix this by
> return ERR_PTR(-EINVAL) if size is 0.
> 
> Signed-off-by: Hailong.Liu <hailong.liu@oppo.com>
> ---
> Changes since v1 [1]:
> - Return ERR_PTR(-EINVAL) or not check IS_ERR_OR_NULL
> 
> BTW,  Barry suggests me that if count is 0, return directly, in my
> opinion, change return value is more resonable.
> 
> [1] https://lore.kernel.org/all/84d7cd03-1cf8-401a-8edf-2524db0bd6d5@oppo.com/
> 
>  mm/vmalloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index a3fedb3ee0db..c430a999805b 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2173,7 +2173,7 @@ static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
>  		 * get_order(0) returns funny result. Just warn and terminate
>  		 * early.
>  		 */
> -		return NULL;
> +		return ERR_PTR(-EINVAL);
>  	}
>  	order = get_order(size);
> 
> --
> 2.34.1
> 
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Uladzislau Rezki