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Subject: Re: [PATCH] wifi: brcmfmac: Adjust n_channels usage for __counted_by
From: Kalle Valo <kvalo@kernel.org>
In-Reply-To: <20240126223150.work.548-kees@kernel.org>
References: <20240126223150.work.548-kees@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: Arend van Spriel <aspriel@gmail.com>, Kees Cook <keescook@chromium.org>,
 Franky Lin <franky.lin@broadcom.com>,
 Hante Meuleman <hante.meuleman@broadcom.com>,
 Chi-hsien Lin <chi-hsien.lin@infineon.com>, Ian Lin <ian.lin@infineon.com>,
 Johannes Berg <johannes.berg@intel.com>,
 Wright Feng <wright.feng@cypress.com>, Hector Martin <marcan@marcan.st>,
 linux-wireless@vger.kernel.org, brcm80211-dev-list.pdl@broadcom.com,
 "Gustavo A. R. Silva" <gustavoars@kernel.org>,
 Linus Walleij <linus.walleij@linaro.org>,
 Jisoo Jang <jisoo.jang@yonsei.ac.kr>, Hans de Goede <hdegoede@redhat.com>,
 Aloka Dixit <quic_alokad@quicinc.com>, John Keeping <john@keeping.me.uk>,
 Jeff Johnson <quic_jjohnson@quicinc.com>, linux-kernel@vger.kernel.org,
 linux-hardening@vger.kernel.org
User-Agent: pwcli/0.1.1-git (https://github.com/kvalo/pwcli/) Python/3.11.2
Message-ID: <170678189299.2736043.11616312910656558919.kvalo@kernel.org>
Date: Thu,  1 Feb 2024 10:04:55 +0000 (UTC)

Kees Cook <keescook@chromium.org> wrote:

> After commit e3eac9f32ec0 ("wifi: cfg80211: Annotate struct
> cfg80211_scan_request with __counted_by"), the compiler may enforce
> dynamic array indexing of req->channels to stay below n_channels. As a
> result, n_channels needs to be increased _before_ accessing the newly
> added array index. Increment it first, then use "i" for the prior index.
> Solves this warning in the coming GCC that has __counted_by support:
> 
> ../drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c: In function 'brcmf_internal_escan_add_info':
> ../drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:3783:46: warning: operation on 'req->
> n_channels' may be undefined [-Wsequence-point]
>  3783 |                 req->channels[req->n_channels++] = chan;
>       |                               ~~~~~~~~~~~~~~~^~
> 
> Fixes: e3eac9f32ec0 ("wifi: cfg80211: Annotate struct cfg80211_scan_request with __counted_by")
> Cc: Arend van Spriel <aspriel@gmail.com>
> Cc: Franky Lin <franky.lin@broadcom.com>
> Cc: Hante Meuleman <hante.meuleman@broadcom.com>
> Cc: Kalle Valo <kvalo@kernel.org>
> Cc: Chi-hsien Lin <chi-hsien.lin@infineon.com>
> Cc: Ian Lin <ian.lin@infineon.com>
> Cc: Johannes Berg <johannes.berg@intel.com>
> Cc: Wright Feng <wright.feng@cypress.com>
> Cc: Hector Martin <marcan@marcan.st>
> Cc: linux-wireless@vger.kernel.org
> Cc: brcm80211-dev-list.pdl@broadcom.com
> Signed-off-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Hans de Goede <hdegoede@redhat.com>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

I'm planning to queue this for wireless tree. Arend, ack?

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20240126223150.work.548-kees@kernel.org/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches