Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210709084351.2087311-1-mudongliangabcd@gmail.com>
In-Reply-To: <20210709084351.2087311-1-mudongliangabcd@gmail.com>
From:   Julian Calaby <julian.calaby@gmail.com>
Date:   Tue, 27 Jul 2021 17:24:44 +1000
Message-ID: <CAGRGNgUNnf=62xnFE4zUiVJ+n6NyGjFUmdR2JChbRkhsDSy0Yw@mail.gmail.com>
Subject: Re: [PATCH] ath9k: hif_usb: fix memory leak in ath9k_hif_usb_firmware_cb
To:     Dongliang Mu <mudongliangabcd@gmail.com>
Cc:     QCA ath9k Development <ath9k-devel@qca.qualcomm.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Brooke Basile <brookebasile@gmail.com>,
        syzbot+6692c72009680f7c4eb2@syzkaller.appspotmail.com,
        linux-wireless <linux-wireless@vger.kernel.org>,
        netdev@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Dongliang,

(Drive-by review, I know almost nothing about the code in question)

On Fri, Jul 9, 2021 at 6:47 PM Dongliang Mu <mudongliangabcd@gmail.com> wrote:
>
> The commit 03fb92a432ea ("ath9k: hif_usb: fix race condition between
> usb_get_urb() and usb_kill_anchored_urbs()") adds three usb_get_urb
> in ath9k_hif_usb_dealloc_tx_urbs and usb_free_urb.
>
> Fix this bug by adding corresponding usb_free_urb in
> ath9k_hif_usb_dealloc_tx_urbs other and hif_usb_stop.
>
> Reported-by: syzbot+6692c72009680f7c4eb2@syzkaller.appspotmail.com
> Fixes: 03fb92a432ea ("ath9k: hif_usb: fix race condition between usb_get_urb() and usb_kill_anchored_urbs()")
> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
> ---
>  drivers/net/wireless/ath/ath9k/hif_usb.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
> index 860da13bfb6a..bda91ff3289b 100644
> --- a/drivers/net/wireless/ath/ath9k/hif_usb.c
> +++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
> @@ -457,6 +457,7 @@ static void hif_usb_stop(void *hif_handle)
>                 usb_kill_urb(tx_buf->urb);
>                 list_del(&tx_buf->list);
>                 usb_free_urb(tx_buf->urb);
> +               usb_free_urb(tx_buf->urb);

Ok, so if I'm reading this correctly, before the first usb_free_urb()
call, we have two references to the urb at tx_buf->urb.

Why?

Isn't the better fix here to detangle why there's more than one
reference to it and resolve it that way? This looks like a hack to fix
something much more fundamentally broken.

Thanks,

-- 
Julian Calaby

Email: julian.calaby@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/