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From: Joe Perches <joe@perches.com>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	Marcel Holtmann <marcel@holtmann.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	"David S. Miller" <davem@davemloft.net>
Cc: linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH][next] Bluetooth: a2mp: Use struct_size() helper
Date: Thu, 07 Feb 2019 20:00:42 -0800
Message-ID: <4faff31066c10285bab0afdb0c1f88f6d3d1a21b.camel@perches.com> (raw)
In-Reply-To: <20190208002817.GA15338@embeddedor>

On Thu, 2019-02-07 at 18:28 -0600, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
> 
> struct foo {
>     int stuff;
>     struct boo entry[];
> };
> 
> size = sizeof(struct foo) + count * sizeof(struct boo);
> instance = alloc(size, GFP_KERNEL)
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> size = struct_size(instance, entry, count);
> instance = alloc(size, GFP_KERNEL)
> 
> This code was detected with the help of Coccinelle.
[]
> diff --git a/net/bluetooth/a2mp.c b/net/bluetooth/a2mp.c
[]
> @@ -174,7 +174,7 @@ static int a2mp_discover_req(struct amp_mgr *mgr, struct sk_buff *skb,
>  			num_ctrl++;
>  	}
>  
> -	len = num_ctrl * sizeof(struct a2mp_cl) + sizeof(*rsp);
> +	len = struct_size(rsp, cl, num_ctrl);
>  	rsp = kmalloc(len, GFP_ATOMIC);
>  	if (!rsp) {
>  		read_unlock(&hci_dev_list_lock);

At least a weakness in this code is len is u16
and struct_size is size_t so there's a size
truncation possible.



  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-08  0:28 Gustavo A. R. Silva
2019-02-08  4:00 ` Joe Perches [this message]
2019-02-08  4:07   ` Gustavo A. R. Silva
2019-02-18 13:02 ` Marcel Holtmann
2019-02-18 17:50   ` Gustavo A. R. Silva

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