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

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Date: Tue, 27 Feb 2024 09:52:44 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Paolo Abeni
 <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com,
 Zhengchao Shao <shaozhengchao@...wei.com>
Subject: Re: [PATCH net-next] netlink: use kvmalloc() in
 netlink_alloc_large_skb()

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;