Return-path: Received: from mail-wm0-f41.google.com ([74.125.82.41]:54541 "EHLO mail-wm0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751378AbeCNM6T (ORCPT ); Wed, 14 Mar 2018 08:58:19 -0400 Received: by mail-wm0-f41.google.com with SMTP id h76so3900489wme.4 for ; Wed, 14 Mar 2018 05:58:18 -0700 (PDT) Subject: Re: [PATCH] brcmfmac: drop Inter-Access Point Protocol packets by default To: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , Kalle Valo References: <20180314110119.13631-1-zajec5@gmail.com> Cc: Franky Lin , Hante Meuleman , Chi-Hsien Lin , Wright Feng , Pieter-Paul Giesberts , James Hughes , linux-wireless@vger.kernel.org, brcm80211-dev-list.pdl@broadcom.com, brcm80211-dev-list@cypress.com, netdev@vger.kernel.org, =?UTF-8?Q?Linus_L=c3=bcssing?= , Felix Fietkau , bridge@lists.linux-foundation.org, =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= From: Arend van Spriel Message-ID: <5AA91C67.90001@broadcom.com> (sfid-20180314_135827_434438_D36D51DA) Date: Wed, 14 Mar 2018 13:58:15 +0100 MIME-Version: 1.0 In-Reply-To: <20180314110119.13631-1-zajec5@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 3/14/2018 12:01 PM, Rafał Miłecki wrote: > From: Rafał Miłecki > > Testing brcmfmac with more recent firmwares resulted in AP interfaces > not working in some specific setups. Debugging resulted in discovering > support for IAPP in Broadcom's firmwares. This is an obsoleted standard > and its implementation is something that: > 1) Most people don't need / want to use > 2) Can allow local DoS attacks > 3) Breaks AP interfaces in some specific bridge setups > > To solve issues it can cause this commit modifies brcmfmac to drop IAPP > packets. If affects: > 1) Rx path: driver won't be sending these unwanted packets up. > 2) Tx path: driver will reject packets that would trigger STA > disassociation perfromed by a firmware (possible local DoS attack). > > It appears there are some Broadcom's clients/users who care about this > feature despite the drawbacks. They can switch it on by a newly added > Kconfig option. Thanks for taking this approach. Looks fine except for .... (see below) Reviewed-by: Arend van Spriel > Signed-off-by: Rafał Miłecki > --- > drivers/net/wireless/broadcom/brcm80211/Kconfig | 20 +++++++++++ > .../wireless/broadcom/brcm80211/brcmfmac/core.c | 39 ++++++++++++++++++++++ > 2 files changed, 59 insertions(+) > > diff --git a/drivers/net/wireless/broadcom/brcm80211/Kconfig b/drivers/net/wireless/broadcom/brcm80211/Kconfig > index 9d99eb42d917..876787ef991a 100644 > --- a/drivers/net/wireless/broadcom/brcm80211/Kconfig > +++ b/drivers/net/wireless/broadcom/brcm80211/Kconfig > @@ -68,6 +68,26 @@ config BRCMFMAC_PCIE > IEEE802.11ac embedded FullMAC WLAN driver. Say Y if you want to > use the driver for an PCIE wireless card. > > +config BRCMFMAC_IAPP > + bool "Partial support for obsoleted Inter-Access Point Protocol" > + depends on BRCMFMAC > + ---help--- > + Most of Broadcom's firmwares can send 802.11f ADD frame every > + time new STA connects to the AP interface. Some recent ones > + can also disassociate STA when they receive such a frame. I do not see any evidence that this would occur only for recent firmware. That stuff is old and not touched recently. > diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c > index 19048526b4af..db6987015fb1 100644 > --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c > +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c [...] > static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff *skb, > struct net_device *ndev) > { > @@ -250,6 +278,12 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff *skb, > goto done; > } > > + if (!IS_ENABLED(CONFIG_BRCMFMAC_IAPP) && brcmf_skb_is_iapp(skb)) { > + dev_kfree_skb(skb); > + ret = -EINVAL; > + goto done; > + } This is not right. The function must return netdev_tx_t type. Here is kerneldoc of .start_xmit(): * netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, * struct net_device *dev); * Called when a packet needs to be transmitted. * Returns NETDEV_TX_OK. Can return NETDEV_TX_BUSY, but you should stop * the queue before that can happen; it's for obsolete devices and weird * corner cases, but the stack really does a non-trivial amount * of useless work if you return NETDEV_TX_BUSY. * Required; cannot be NULL. You may want to increase dropped netstat or add driver internal statistic counter so there is visibility of IAPP packets being dropped. Regards, Arend