linux-kernel - Re: [PATCH v3 2/2] wifi: ath9k: protect WMI command response buffer replacement with a lock

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Date:   Tue, 08 Aug 2023 16:07:57 +0200
From:   Toke Høiland-Jørgensen <toke@...e.dk>
To:     Fedor Pchelkin <pchelkin@...ras.ru>, Kalle Vallo <kvalo@...nel.org>
Cc:     Fedor Pchelkin <pchelkin@...ras.ru>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Senthil Balasubramanian <senthilkumar@...eros.com>,
        "John W. Linville" <linville@...driver.com>,
        Vasanthakumar Thiagarajan <vasanth@...eros.com>,
        Sujith <Sujith.Manoharan@...eros.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        lvc-project@...uxtesting.org,
        syzbot+f2cb6e0ffdb961921e4d@...kaller.appspotmail.com,
        Hillf Danton <hdanton@...a.com>
Subject: Re: [PATCH v3 2/2] wifi: ath9k: protect WMI command response buffer
 replacement with a lock

Fedor Pchelkin <pchelkin@...ras.ru> writes:

> If ath9k_wmi_cmd() has exited with a timeout, it is possible that during
> next ath9k_wmi_cmd() call the wmi_rsp callback for previous wmi command
> writes to new wmi->cmd_rsp_buf and makes a completion. This results in an
> invalid ath9k_wmi_cmd() return value.
>
> Move the replacement of WMI command response buffer and length under
> wmi_lock. Note that last_seq_id value is updated there, too.
>
> Thus, the buffer cannot be written to by a belated wmi_rsp callback
> because that path is properly rejected by the last_seq_id check.
>
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
>
> Fixes: fb9987d0f748 ("ath9k_htc: Support for AR9271 chipset.")
> Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>

Given that the previous patch resets the last_seq_id to 0 on timeout
under the lock, I don't think this patch is strictly necessary anymore.
However, it doesn't hurt either, and I actually think moving the update
of the rsp buf into ath9k_wmi_cmd_issue() aids readability, so:

Acked-by: Toke Høiland-Jørgensen <toke@...e.dk>