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

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Message-ID: <ZsZWxnfy21CpOLoR@smile.fi.intel.com>
Date: Thu, 22 Aug 2024 00:06:14 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: "Gustavo A. R. Silva" <gustavo@...eddedor.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 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.)

-- 
With Best Regards,
Andy Shevchenko