linux-kernel - Re: [PATCH 1/1] mwifiex: Fix possible buffer overflows in mwifiex_config

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Message-ID: <CAGRGNgWzTnmyYO97MkW+biQBrs-LarknCAsM9q+-UMqcSCN3bQ@mail.gmail.com>
Date:   Wed, 9 Dec 2020 11:36:05 +1100
From:   Julian Calaby <julian.calaby@...il.com>
To:     Xiaohui Zhang <ruc_zhangxiaohui@....com>
Cc:     Amitkumar Karwar <amitkarwar@...il.com>,
        Ganapathi Bhat <ganapathi.bhat@....com>,
        Xinming Hu <huxinming820@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] mwifiex: Fix possible buffer overflows in mwifiex_config_scan

Hi Xiaohui,

On Wed, Dec 9, 2020 at 12:07 AM Xiaohui Zhang <ruc_zhangxiaohui@....com> wrote:
>
> From: Zhang Xiaohui <ruc_zhangxiaohui@....com>
>
> mwifiex_config_scan() calls memcpy() without checking
> the destination size may trigger a buffer overflower,
> which a local user could use to cause denial of service
> or the execution of arbitrary code.
> Fix it by putting the length check before calling memcpy().
>
> Signed-off-by: Zhang Xiaohui <ruc_zhangxiaohui@....com>
> ---
>  drivers/net/wireless/marvell/mwifiex/scan.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c b/drivers/net/wireless/marvell/mwifiex/scan.c
> index c2a685f63..b1d90678f 100644
> --- a/drivers/net/wireless/marvell/mwifiex/scan.c
> +++ b/drivers/net/wireless/marvell/mwifiex/scan.c
> @@ -930,6 +930,8 @@ mwifiex_config_scan(struct mwifiex_private *priv,
>                                     "DIRECT-", 7))
>                                 wildcard_ssid_tlv->max_ssid_length = 0xfe;
>
> +                       if (ssid_len > 1)
> +                               ssid_len = 1;
>                         memcpy(wildcard_ssid_tlv->ssid,
>                                user_scan_in->ssid_list[i].ssid, ssid_len);

Can ssid_len ever be 0 here?

If it can't, should we just set ssid_len to 1 unconditionally?

If it can, should we just skip the memcpy as it won't do anything?

Thanks,

-- 
Julian Calaby

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