linux-kernel - RE: [PATCH v2 next] wifi: rtw89: mcc: prevent shift wrapping in rtw89_core_mlsr

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Message-ID: <a46c420109f0440a987d28c531dd39d6@realtek.com>
Date: Thu, 29 May 2025 02:15:03 +0000
From: Zong-Zhe Yang <kevin_yang@...ltek.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
CC: Ping-Ke Shih <pkshih@...ltek.com>,
        "linux-wireless@...r.kernel.org"
	<linux-wireless@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org"
	<kernel-janitors@...r.kernel.org>
Subject: RE: [PATCH v2 next] wifi: rtw89: mcc: prevent shift wrapping in rtw89_core_mlsr_switch()

Dan Carpenter <dan.carpenter@...aro.org> wrote:
> 
> The "link_id" value comes from the user via debugfs.  If it's larger than BITS_PER_LONG then
> that would result in shift wrapping and potentially an out of bounds access later.  In fact, we
> can limit it to IEEE80211_MLD_MAX_NUM_LINKS (15).
> 
> Fortunately, only root can write to debugfs files so the security impact is minimal.
> 
> Fixes: 9dd85e739ce0 ("wifi: rtw89: debug: add mlo_mode dbgfs")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
> Use IEEE80211_MLD_MAX_NUM_LINKS as a limit instead of BITS_PER_LONG.
> It's stricter and also more informative.
> 
>  drivers/net/wireless/realtek/rtw89/core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtw89/core.c
> b/drivers/net/wireless/realtek/rtw89/core.c
> index 49447668cbf3..3604a8e15df0 100644
> --- a/drivers/net/wireless/realtek/rtw89/core.c
> +++ b/drivers/net/wireless/realtek/rtw89/core.c
> @@ -5239,7 +5239,8 @@ int rtw89_core_mlsr_switch(struct rtw89_dev *rtwdev, struct
> rtw89_vif *rtwvif,
>         if (unlikely(!ieee80211_vif_is_mld(vif)))
>                 return -EOPNOTSUPP;
> 
> -       if (unlikely(!(usable_links & BIT(link_id)))) {
> +       if (unlikely(link_id >= IEEE80211_MLD_MAX_NUM_LINKS ||
> +                    !(usable_links & BIT(link_id)))) {
>                 rtw89_warn(rtwdev, "%s: link id %u is not usable\n", __func__,
>                            link_id);
>                 return -ENOLINK;
> --
> 2.47.2

It looks good to me.
Thank you.