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Date: Fri, 2 Feb 2024 10:58:45 +0100
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Subject: Re: [PATCH] wifi: brcmfmac: Adjust n_channels usage for __counted_by
To: Kalle Valo <kvalo@kernel.org>, Kees Cook <keescook@chromium.org>
Cc: 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
References: <20240126223150.work.548-kees@kernel.org>
 <170678189299.2736043.11616312910656558919.kvalo@kernel.org>
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From: Arend Van Spriel <aspriel@gmail.com>
In-Reply-To: <170678189299.2736043.11616312910656558919.kvalo@kernel.org>
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On 2/1/2024 11:04 AM, Kalle Valo wrote:
> 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?

This slipped past my broadcom email. As the Fixes commit is in 6.7 I 
would say ACK.

Gr. AvS