linux-hardening - Re: [PATCH 4/7] wifi: cfg80211: Annotate struct cfg80211_pmsr_request with __counted

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Date:   Thu, 17 Aug 2023 15:24:15 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Kees Cook <keescook@...omium.org>,
        Johannes Berg <johannes@...solutions.net>
Cc:     "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,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 4/7] wifi: cfg80211: Annotate struct cfg80211_pmsr_request
 with __counted_by



On 8/17/23 15:15, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct cfg80211_pmsr_request.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> 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

> ---
>   include/net/cfg80211.h | 2 +-
>   net/wireless/pmsr.c    | 3 +--
>   2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> index 5c7d091b3925..e9ca4726a732 100644
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -3948,7 +3948,7 @@ struct cfg80211_pmsr_request {
>   
>   	struct list_head list;
>   
> -	struct cfg80211_pmsr_request_peer peers[];
> +	struct cfg80211_pmsr_request_peer peers[] __counted_by(n_peers);
>   };
>   
>   /**
> diff --git a/net/wireless/pmsr.c b/net/wireless/pmsr.c
> index 77000a264855..9611aa0bd051 100644
> --- a/net/wireless/pmsr.c
> +++ b/net/wireless/pmsr.c
> @@ -291,6 +291,7 @@ int nl80211_pmsr_start(struct sk_buff *skb, struct genl_info *info)
>   	req = kzalloc(struct_size(req, peers, count), GFP_KERNEL);
>   	if (!req)
>   		return -ENOMEM;
> +	req->n_peers = count;
>   
>   	if (info->attrs[NL80211_ATTR_TIMEOUT])
>   		req->timeout = nla_get_u32(info->attrs[NL80211_ATTR_TIMEOUT]);
> @@ -321,8 +322,6 @@ int nl80211_pmsr_start(struct sk_buff *skb, struct genl_info *info)
>   			goto out_err;
>   		idx++;
>   	}
> -
> -	req->n_peers = count;
>   	req->cookie = cfg80211_assign_cookie(rdev);
>   	req->nl_portid = info->snd_portid;
>