Re: [PATCH net-next] netlink: use kvmalloc() in netlink_alloc_large_skb()

From: Jakub Kicinski <kuba@kernel.org>
To: Eric Dumazet <edumazet@google.com>
Cc: "David S . Miller" <davem@davemloft.net>,
	Paolo Abeni <pabeni@redhat.com>,
	netdev@vger.kernel.org, eric.dumazet@gmail.com,
	Zhengchao Shao <shaozhengchao@huawei.com>
Subject: Re: [PATCH net-next] netlink: use kvmalloc() in netlink_alloc_large_skb()
Date: Tue, 27 Feb 2024 09:52:44 -0800	[thread overview]
Message-ID: <20240227095244.23e5a740@kernel.org> (raw)
In-Reply-To: <20240224090630.605917-1-edumazet@google.com>

On Sat, 24 Feb 2024 09:06:30 +0000 Eric Dumazet wrote:
>  struct sk_buff *netlink_alloc_large_skb(unsigned int size, int broadcast)
>  {
> +	size_t head_size = SKB_HEAD_ALIGN(size);
>  	struct sk_buff *skb;
>  	void *data;
>  
> -	if (size <= NLMSG_GOODSIZE || broadcast)
> +	if (head_size <= PAGE_SIZE || broadcast)
>  		return alloc_skb(size, GFP_KERNEL);
>  
> -	size = SKB_DATA_ALIGN(size) +
> -	       SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> -
> -	data = vmalloc(size);
> -	if (data == NULL)
> +	data = kvmalloc(head_size, GFP_KERNEL);
> +	if (!data)
>  		return NULL;
>  
> -	skb = __build_skb(data, size);
> -	if (skb == NULL)
> -		vfree(data);
> -	else
> +	skb = __build_skb(data, head_size);

Is this going to work with KFENCE? Don't we need similar size
adjustment logic as we have in __slab_build_skb() ?

> +	if (!skb)
> +		kvfree(data);
> +	else if (is_vmalloc_addr(data))
>  		skb->destructor = netlink_skb_destructor;