linux-hardening - Re: [PATCH][next] wifi: mwifiex: Replace one-element arrays with flexible-array members

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Message-ID: <0627c008-a3f9-4b2e-a3b9-72c6a1a287b0@embeddedor.com>
Date: Wed, 21 Aug 2024 15:25:52 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Amitkumar Karwar <amitkarwar@...il.com>,
 Ganapathi Bhat <ganapathi017@...il.com>,
 Sharvari Harisangam <sharvari.harisangam@....com>,
 Xinming Hu <huxinming820@...il.com>, Kalle Valo <kvalo@...nel.org>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] wifi: mwifiex: Replace one-element arrays with
 flexible-array members



On 21/08/24 15:06, Andy Shevchenko wrote:
> On Wed, Aug 21, 2024 at 02:59:34PM -0600, Gustavo A. R. Silva wrote:
>> On 21/08/24 14:26, Andy Shevchenko wrote:
>>> On Thu, Feb 02, 2023 at 07:32:00PM -0600, Gustavo A. R. Silva wrote:
>>>> One-element arrays are deprecated, and we are replacing them with flexible
>>>> array members instead. So, replace one-element arrays with flexible-array
>>>> members in multiple structures.
>>>>
>>>> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
>>>> routines on memcpy() and help us make progress towards globally
>>>> enabling -fstrict-flex-arrays=3 [1].
>>>>
>>>> This results in no differences in binary output.
>>>
>>> Sorry for blast from the past, but I have a question here.
>>>
>>> This change seems converts many of the flexible arrays in this driver.
>>> But what's behind this one?
>>>
>>> struct host_cmd_ds_802_11_scan_ext {
>>>           u32   reserved;
>>>           u8    tlv_buffer[1];
>>> } __packed;
>>>
>>>
>>> AFAIU this needs also some care. On the real machine I have got this
>>>
>>> elo 16 17:51:58 surfacebook kernel: ------------[ cut here ]------------
>>> elo 16 17:51:58 surfacebook kernel: memcpy: detected field-spanning write (size 243) of single field "ext_scan->tlv_buffer" at drivers/net/wireless/marvell/mwifiex/scan.c:2239 (size 1)
>>> elo 16 17:51:58 surfacebook kernel: WARNING: CPU: 0 PID: 498 at drivers/net/wireless/marvell/mwifiex/scan.c:2239 mwifiex_cmd_802_11_scan_ext+0x83/0x90 [mwifiex]
>>>
>>> which leads to
>>>
>>>           memcpy(ext_scan->tlv_buffer, scan_cfg->tlv_buf, scan_cfg->tlv_buf_len);
>>>
>>> but the code allocates 2k or more for the command buffer, so this seems
>>> quite enough for 243 bytes.
>>>
>>
>> I think this would do it:
> 
> Thank you for the prompt respond! Can you send it as a formal patch?
> Or do you want me to test it first? (If the second one, it might take
> weeks as this is my home laptop that I don't reboot too often. I think
> it's can be sent anyway.)
> 

Done:
https://lore.kernel.org/linux-hardening/ZsZa5xRcsLq9D+RX@elsanto/

Thanks for reporting this. :)
--
Gustavo