From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: Re: [PATCH] iwlwifi: d3: use struct_size() in kzalloc()
Date: Fri, 24 Aug 2018 06:58:05 -0500
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Cc: Johannes Berg <johannes.berg@intel.com>,
        Emmanuel Grumbach <emmanuel.grumbach@intel.com>,
        Luca Coelho <luciano.coelho@intel.com>,
        Intel Linux Wireless <linuxwifi@intel.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
To: Joe Perches <joe@perches.com>, Kees Cook <keescook@chromium.org>
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Hi Joe,

On 8/23/18 11:33 PM, Joe Perches wrote:
> On Thu, 2018-08-23 at 20:03 -0700, Kees Cook wrote:
>> On Thu, Aug 23, 2018 at 6:15 PM, Gustavo A. R. Silva
>> <gustavo@embeddedor.com> 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;
>>>         void *entry[];
>>> };
> 
> Question for Gustavo.
> 
> Did you find any existing instances that are miscalculated?
> 

I found the following bug:

https://lore.kernel.org/patchwork/patch/977357/


> I believe there are some cases like:
> 
> 	size = sizeof(struct foo) + count * sizeof(something);
> 	ptr = kmalloc(size);
> 	memset(ptr + sizeof(struct foo), 0, size - sizeof(struct foo));
> 
> where something could go wrong and not be detected.
> 

It might be worth it to write a Coccinelle script for this.

--
Gustavo