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Subject: Re: [PATCH] rtw88: hold RCU lock when calling
 ieee80211_find_sta_by_ifaddr()
To:     Shuah Khan <skhan@linuxfoundation.org>, tony0620emma@gmail.com,
        kvalo@codeaurora.org, davem@davemloft.net, kuba@kernel.org
Cc:     linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <cover.1613090339.git.skhan@linuxfoundation.org>
 <1cfa036227cfa9fdd04316c01e1d754f13a70d9e.1613090339.git.skhan@linuxfoundation.org>
 <20210212021312.40486-2-skhan@linuxfoundation.org>
From:   Felix Fietkau <nbd@nbd.name>
Message-ID: <0dfbd38e-6158-4162-cbd6-90e89728860e@nbd.name>
Date:   Fri, 12 Feb 2021 07:34:44 +0100
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On 2021-02-12 03:13, Shuah Khan wrote:
> ieee80211_find_sta_by_ifaddr() must be called under the RCU lock and
> the resulting pointer is only valid under RCU lock as well.
> 
> Fix rtw_rx_addr_match_iter() to hold RCU read lock before it calls
> ieee80211_find_sta_by_ifaddr() and release it when the resulting
> pointer is no longer needed.
> 
> This problem was found while reviewing code to debug RCU warn from
> ath10k_wmi_tlv_parse_peer_stats_info() and a subsequent manual audit
> of other callers of ieee80211_find_sta_by_ifaddr() that don't hold
> RCU read lock.
> 
> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
This one also seems unnecessary. rtw_rx_addr_match_iter is called by
ieee80211_iterate_active_interfaces_atomic, which acquires the RCU read
lock before calling it.

- Felix