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

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Message-ID: <fb9ec7de-7c8a-4e94-94c2-eeea6369550e@embeddedor.com>
Date: Tue, 6 Feb 2024 14:32:32 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Kees Cook <keescook@...omium.org>, Brian Norris <briannorris@...omium.org>
Cc: 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 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);

--
Gustavo

> diff --git a/drivers/net/wireless/marvell/mwifiex/fw.h b/drivers/net/wireless/marvell/mwifiex/fw.h
> index 62f3c9a52a1d..3adc447b715f 100644
> --- a/drivers/net/wireless/marvell/mwifiex/fw.h
> +++ b/drivers/net/wireless/marvell/mwifiex/fw.h
> @@ -770,7 +770,7 @@ struct mwifiex_chan_scan_param_set {
>   
>   struct mwifiex_ie_types_chan_list_param_set {
>   	struct mwifiex_ie_types_header header;
> -	struct mwifiex_chan_scan_param_set chan_scan_param[1];
> +	struct mwifiex_chan_scan_param_set chan_scan_param[];
>   } __packed;
>   
>   struct mwifiex_ie_types_rxba_sync {
> diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c b/drivers/net/wireless/marvell/mwifiex/scan.c
> index a2ddac363b10..0326b121747c 100644
> --- a/drivers/net/wireless/marvell/mwifiex/scan.c
> +++ b/drivers/net/wireless/marvell/mwifiex/scan.c
> @@ -664,15 +664,14 @@ mwifiex_scan_channel_list(struct mwifiex_private *priv,
>   
>   			/* Copy the current channel TLV to the command being
>   			   prepared */
> -			memcpy(chan_tlv_out->chan_scan_param + tlv_idx,
> +			memcpy(&chan_tlv_out->chan_scan_param[tlv_idx],
>   			       tmp_chan_list,
> -			       sizeof(chan_tlv_out->chan_scan_param));
> +			       sizeof(*chan_tlv_out->chan_scan_param));
>   
>   			/* Increment the TLV header length by the size
>   			   appended */
>   			le16_unaligned_add_cpu(&chan_tlv_out->header.len,
> -					       sizeof(
> -						chan_tlv_out->chan_scan_param));
> +					       sizeof(*chan_tlv_out->chan_scan_param));
>   
>   			/*
>   			 * The tlv buffer length is set to the number of bytes
> @@ -2369,12 +2368,11 @@ int mwifiex_cmd_802_11_bg_scan_config(struct mwifiex_private *priv,
>   		     chan_idx < MWIFIEX_BG_SCAN_CHAN_MAX &&
>   		     bgscan_cfg_in->chan_list[chan_idx].chan_number;
>   		     chan_idx++) {
> -			temp_chan = chan_list_tlv->chan_scan_param + chan_idx;
> +			temp_chan = &chan_list_tlv->chan_scan_param[chan_idx];
>   
>   			/* Increment the TLV header length by size appended */
>   			le16_unaligned_add_cpu(&chan_list_tlv->header.len,
> -					       sizeof(
> -					       chan_list_tlv->chan_scan_param));
> +					       sizeof(*chan_list_tlv->chan_scan_param));
>   
>   			temp_chan->chan_number =
>   				bgscan_cfg_in->chan_list[chan_idx].chan_number;
> @@ -2413,7 +2411,7 @@ int mwifiex_cmd_802_11_bg_scan_config(struct mwifiex_private *priv,
>   							   chan_scan_param);
>   		le16_unaligned_add_cpu(&chan_list_tlv->header.len,
>   				       chan_num *
> -			     sizeof(chan_list_tlv->chan_scan_param[0]));
> +			     sizeof(*chan_list_tlv->chan_scan_param));
>   	}
>   
>   	tlv_pos += (sizeof(chan_list_tlv->header)