linux-kernel - Re: [PATCH] wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config

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Message-ID: <ZumuvP3aHiHHzGjp@smile.fi.intel.com>
Date: Tue, 17 Sep 2024 19:30:52 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Alper Nebi Yasak <alpernebiyasak@...il.com>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Lin <yu-hao.lin@....com>,
	Dmitry Antipov <dmantipov@...dex.ru>,
	Brian Norris <briannorris@...omium.org>,
	Kalle Valo <kvalo@...nel.org>,
	Francesco Dolcini <francesco@...cini.it>,
	Sascha Hauer <s.hauer@...gutronix.de>, Kees Cook <kees@...nel.org>,
	"Gustavo A . R . Silva" <gustavoars@...nel.org>,
	Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH] wifi: mwifiex: Fix memcpy() field-spanning write warning
 in mwifiex_config_scan()

On Tue, Sep 17, 2024 at 06:08:41PM +0300, Alper Nebi Yasak wrote:
> Replace one-element array with a flexible-array member in `struct
> mwifiex_ie_types_wildcard_ssid_params` to fix the following warning
> on a MT8173 Chromebook (mt8173-elm-hana):
> 
> [  356.775250] ------------[ cut here ]------------
> [  356.784543] memcpy: detected field-spanning write (size 6) of single field "wildcard_ssid_tlv->ssid" at drivers/net/wireless/marvell/mwifiex/scan.c:904 (size 1)
> [  356.813403] WARNING: CPU: 3 PID: 742 at drivers/net/wireless/marvell/mwifiex/scan.c:904 mwifiex_scan_networks+0x4fc/0xf28 [mwifiex]
> 
> The "(size 6)" above is exactly the length of the SSID of the network
> this device was connected to. The source of the warning looks like:
> 
>     ssid_len = user_scan_in->ssid_list[i].ssid_len;
>     [...]
>     memcpy(wildcard_ssid_tlv->ssid,
>            user_scan_in->ssid_list[i].ssid, ssid_len);
> 
> Also adjust a #define that uses sizeof() on this struct to keep the
> value same as before.

...

>  #define WILDCARD_SSID_TLV_MAX_SIZE  \
>  	(MWIFIEX_MAX_SSID_LIST_LENGTH *					\
>  		(sizeof(struct mwifiex_ie_types_wildcard_ssid_params)	\
> -			+ IEEE80211_MAX_SSID_LEN))
> +			+ IEEE80211_MAX_SSID_LEN + 1))
>  

This hunk has to be carefully checked by wireless people. I'm not sure
that we need  + 1 here.

Otherwise, LGTM.

-- 
With Best Regards,
Andy Shevchenko