linux-hardening - Re: [PATCH v2] wifi: nl80211: Split memcpy() of struct nl80211_wowlan_tcp_data

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Message-ID: <YzNTJ4D8HyeIvSiR@work>
Date:   Tue, 27 Sep 2022 14:46:47 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Johannes Berg <johannes@...solutions.net>,
        "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 v2] wifi: nl80211: Split memcpy() of struct
 nl80211_wowlan_tcp_data_token flexible array

On Mon, Sep 26, 2022 at 07:29:23PM -0700, Kees Cook wrote:
> To work around a misbehavior of the compiler's ability to see into
> composite flexible array structs (as detailed in the coming memcpy()
> hardening series[1]), split the memcpy() of the header and the payload
> so no false positive run-time overflow warning will be generated.
> 
> [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org/
> 
> Cc: Johannes Berg <johannes@...solutions.net>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: linux-wireless@...r.kernel.org
> Cc: netdev@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks!
--
Gustavo

> ---
> v2: - fix typo leading "+" (Gustavo)
> v1: https://lore.kernel.org/lkml/20220927003903.1941873-1-keescook@chromium.org
> ---
>  net/wireless/nl80211.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
> index 2705e3ee8fc4..169e3ec33466 100644
> --- a/net/wireless/nl80211.c
> +++ b/net/wireless/nl80211.c
> @@ -13171,7 +13171,9 @@ static int nl80211_parse_wowlan_tcp(struct cfg80211_registered_device *rdev,
>  	       wake_mask_size);
>  	if (tok) {
>  		cfg->tokens_size = tokens_size;
> -		memcpy(&cfg->payload_tok, tok, sizeof(*tok) + tokens_size);
> +		cfg->payload_tok = *tok;
> +		memcpy(cfg->payload_tok.token_stream, tok->token_stream,
> +		       tokens_size);
>  	}
>  
>  	trig->tcp = cfg;
> -- 
> 2.34.1
>