linux-hardening - Re: [PATCH v2] wifi: mwifiex: Refactor 1-element array into flexible array in struct mwifiex_ie_types_chan_list_param

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Date: Wed, 7 Feb 2024 01:56:55 -0800
From: Kees Cook <keescook@...omium.org>
To: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc: Brian Norris <briannorris@...omium.org>, Kalle Valo <kvalo@...nel.org>,
	Dmitry Antipov <dmantipov@...dex.ru>,
	Johannes Berg <johannes.berg@...el.com>,
	zuoqilin <zuoqilin@...ong.com>, Ruan Jinjie <ruanjinjie@...wei.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	"Gustavo A . R . Silva" <gustavoars@...nel.org>,
	linux-wireless@...r.kernel.org, Dan Carpenter <error27@...il.com>,
	Rafael Beims <rafael.beims@...adex.com>,
	David Lin <yu-hao.lin@....com>, Lukas Wunner <lukas@...ner.de>,
	Simon Horman <horms@...nel.org>, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] wifi: mwifiex: Refactor 1-element array into flexible
 array in struct mwifiex_ie_types_chan_list_param_set

On Tue, Feb 06, 2024 at 02:32:32PM -0600, Gustavo A. R. Silva wrote:
> 
> 
> On 2/6/24 12:39, Kees Cook wrote:
> > struct mwifiex_ie_types_chan_list_param_set::chan_scan_param is treated
> > as a flexible array, so convert it into one so that it doesn't trip the
> > array bounds sanitizer[1]. Only once place was using sizeof() on the
> > whole struct (in 11n.c), so adjust it to follow the calculation pattern
> > used by scan.c to avoid including the trailing single element.
> > 
> > Link: https://github.com/KSPP/linux/issues/51 [1]
> > Cc: Brian Norris <briannorris@...omium.org>
> > Cc: Kalle Valo <kvalo@...nel.org>
> > Cc: Dmitry Antipov <dmantipov@...dex.ru>
> > Cc: Johannes Berg <johannes.berg@...el.com>
> > Cc: zuoqilin <zuoqilin@...ong.com>
> > Cc: Ruan Jinjie <ruanjinjie@...wei.com>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> > Cc: Gustavo A. R. Silva <gustavoars@...nel.org>
> > Cc: linux-wireless@...r.kernel.org
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > ---
> >   drivers/net/wireless/marvell/mwifiex/11n.c  |  8 +++-----
> >   drivers/net/wireless/marvell/mwifiex/fw.h   |  2 +-
> >   drivers/net/wireless/marvell/mwifiex/scan.c | 14 ++++++--------
> >   3 files changed, 10 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/net/wireless/marvell/mwifiex/11n.c b/drivers/net/wireless/marvell/mwifiex/11n.c
> > index 90e401100898..9ed90da4dfcf 100644
> > --- a/drivers/net/wireless/marvell/mwifiex/11n.c
> > +++ b/drivers/net/wireless/marvell/mwifiex/11n.c
> > @@ -392,12 +392,10 @@ mwifiex_cmd_append_11n_tlv(struct mwifiex_private *priv,
> >   		chan_list =
> >   			(struct mwifiex_ie_types_chan_list_param_set *) *buffer;
> > -		memset(chan_list, 0,
> > -		       sizeof(struct mwifiex_ie_types_chan_list_param_set));
> > +		memset(chan_list, 0, struct_size(chan_list, chan_scan_param, 1));
> >   		chan_list->header.type = cpu_to_le16(TLV_TYPE_CHANLIST);
> > -		chan_list->header.len = cpu_to_le16(
> > -			sizeof(struct mwifiex_ie_types_chan_list_param_set) -
> > -			sizeof(struct mwifiex_ie_types_header));
> > +		chan_list->header.len =
> > +			cpu_to_le16(sizeof(struct mwifiex_chan_scan_param_set));
> >   		chan_list->chan_scan_param[0].chan_number =
> >   			bss_desc->bcn_ht_oper->primary_chan;
> >   		chan_list->chan_scan_param[0].radio_type =
> This probably still needs a bit more work.
> 
> There are a couple more instances of `sizeof()` that should probably be
> audited and adjusted:
> 
> drivers/net/wireless/marvell/mwifiex/11n.c:414:         *buffer += sizeof(struct mwifiex_ie_types_chan_list_param_set);
> drivers/net/wireless/marvell/mwifiex/11n.c:415:         ret_len += sizeof(struct mwifiex_ie_types_chan_list_param_set);

Good call. I think this is the right delta:

-               *buffer += sizeof(struct mwifiex_ie_types_chan_list_param_set);
-               ret_len += sizeof(struct mwifiex_ie_types_chan_list_param_set);
+               *buffer += struct_size(chan_list, chan_scan_param, 1);
+               ret_len += struct_size(chan_list, chan_scan_param, 1);

I will send a v3.

-- 
Kees Cook