Return-path: Received: from 8.mo1.mail-out.ovh.net ([178.33.110.239]:54350 "EHLO 8.mo1.mail-out.ovh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750950AbeCNQ6f (ORCPT ); Wed, 14 Mar 2018 12:58:35 -0400 Received: from player737.ha.ovh.net (unknown [10.109.108.206]) by mo1.mail-out.ovh.net (Postfix) with ESMTP id 86CBEDFFF3 for ; Wed, 14 Mar 2018 16:39:23 +0100 (CET) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Date: Wed, 14 Mar 2018 16:39:04 +0100 From: =?UTF-8?Q?Rafa=C5=82_Mi=C5=82ecki?= To: Arend van Spriel Cc: =?UTF-8?Q?Rafa=C5=82_Mi=C5=82ecki?= , Kalle Valo , 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 Subject: Re: [PATCH] brcmfmac: drop Inter-Access Point Protocol packets by default In-Reply-To: <5AA91C67.90001@broadcom.com> References: <20180314110119.13631-1-zajec5@gmail.com> <5AA91C67.90001@broadcom.com> Message-ID: (sfid-20180314_175902_432803_972C26FB) Sender: linux-wireless-owner@vger.kernel.org List-ID: On 2018-03-14 13:58, Arend van Spriel wrote: > 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. My evidence is comparing firmwares for 4366b1: 10.10.69.3309 (r610991) vs. 10.10 (TOB) (r663589). The first one is from linux-firmware.git and it doesn't implement IAPP in the TX path. The later one is what I got from you privately and it implements it. Also a firmware for 4366c0: 10.10.122.20 (r683106) which is relatively new implements IAPP in the TX path. >> 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. Please take a closer look at how brcmf_netdev_start_xmit() works. Above code *will* return netdev_tx_t. > You may want to increase dropped netstat or add driver internal > statistic counter so there is visibility of IAPP packets being > dropped. OK, I'll try to find a stat to increase.