Subject: Re: [PATCH V2] brcmfmac: fix possible buffer overflow in brcmf_cfg80211_mgmt_tx()

From: Arend van Spriel <arend.vanspriel-dY08KVG/lbpWk0Htik3J/[email-masked]>
Date: Wed, 12 Jul 2017 13:49:23 +0200

On 7/7/2017 10:09 PM, Arend van Spriel wrote:
> The lower level nl80211 code in cfg80211 ensures that "len" is between
> 25 and NL80211_ATTR_FRAME (2304).  We subtract DOT11_MGMT_HDR_LEN (24) from
> "len" so thats's max of 2280.  However, the action_frame->data[] buffer is
> only BRCMF_FIL_ACTION_FRAME_SIZE (1800) bytes long so this memcpy() can
> overflow.
>
> 	memcpy(action_frame->data, &buf[DOT11_MGMT_HDR_LEN],
> 	       le16_to_cpu(action_frame->len));
>
> Cc: [email-masked] # 3.9.x
> Fixes: 18e2f61db3b70 ("brcmfmac: P2P action frame tx.")
> Reported-by: "freenerguo(郭大兴)" <[email-masked]>
> Signed-off-by: Arend van Spriel <arend.vanspriel-dY08KVG/lbpWk0Htik3J/[email-masked]>
> ---
>   V2:
>    - added Fixes: tag and Cc: for stable kernels.
>    - Cc: patch to netdev list.
> ---
> Hi David,
>
> Here is the patch as Linus send it to us and [email-masked] I
> removed the lower bound check as that is already done in cfg80211.
> Now I signed off on the patch although formally I suppose Linus should
> sign it off. Putting it out there so people can respond as deemed
> necessary.
>
> The reason for submitting it to your tree is the fact that Kalle is
> on vacation for next 10 days or so which was indicated to me by Johannes.
> The patch applies to the master branch of your net repository. For
> reference V1 of this patch can be found here [1].

Hi Dave,

Not sure if you missed this one. It is addressing a reported security 
issue and intended for the net repository, not net-next which is 
obviously closed [2].

Regards,
Arend

[2] http://vger.kernel.org/~davem/net-next.html

> Regards,
> Arend
>
> [1] https://patchwork.kernel.org/patch/9829977/
> ---
>   drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> index cd1d673..d182a00 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> @@ -4851,6 +4851,11 @@ static int brcmf_cfg80211_stop_ap(struct wiphy *wiphy, struct net_device *ndev)
>   		cfg80211_mgmt_tx_status(wdev, *cookie, buf, len, true,
>   					GFP_KERNEL);
>   	} else if (ieee80211_is_action(mgmt->frame_control)) {
> +		if (len > BRCMF_FIL_ACTION_FRAME_SIZE + DOT11_MGMT_HDR_LEN) {
> +			brcmf_err("invalid action frame length\n");
> +			err = -EINVAL;
> +			goto exit;
> +		}
>   		af_params = kzalloc(sizeof(*af_params), GFP_KERNEL);
>   		if (af_params == NULL) {
>   			brcmf_err("unable to allocate frame\n");
>