Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:48593 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933680AbaDVSAT (ORCPT ); Tue, 22 Apr 2014 14:00:19 -0400 Date: Tue, 22 Apr 2014 13:53:22 -0400 From: "John W. Linville" To: Felix Fietkau Cc: greearb@candelatech.com, ath9k-devel@venema.h4ckr.net, linux-wireless@vger.kernel.org Subject: Re: [PATCH] ath9k: Prevent divide by zero kernel crash. Message-ID: <20140422175322.GA16193@tuxdriver.com> (sfid-20140422_200039_192642_709DF2BC) References: <1397695240-13710-1-git-send-email-greearb@candelatech.com> <534F870E.80209@openwrt.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <534F870E.80209@openwrt.org> Sender: linux-wireless-owner@vger.kernel.org List-ID: Please consider Felix's comments while refactoring this for the current code structure... John On Thu, Apr 17, 2014 at 09:47:26AM +0200, Felix Fietkau wrote: > On 2014-04-17 02:40, greearb@candelatech.com wrote: > > From: Ben Greear > > > > Make sure we cannot ever assign beacon interval to zero. > > > > Signed-off-by: Ben Greear > > --- > > drivers/net/wireless/ath/ath9k/beacon.c | 4 ++++ > > drivers/net/wireless/ath/ath9k/recv.c | 3 ++- > > 2 files changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/net/wireless/ath/ath9k/beacon.c b/drivers/net/wireless/ath/ath9k/beacon.c > > index 2e8bba0..5391f01 100644 > > --- a/drivers/net/wireless/ath/ath9k/beacon.c > > +++ b/drivers/net/wireless/ath/ath9k/beacon.c > > @@ -443,6 +443,8 @@ static u32 ath9k_mod_tsf64_tu(u64 tsf, u32 div_tu) > > { > > u32 tsf_mod, tsf_hi, tsf_lo, mod_hi, mod_lo; > > > > + if (WARN_ON_ONCE(div_tu == 0)) > > + div_tu = 100; > > tsf_mod = tsf & (BIT(10) - 1); > > tsf_hi = tsf >> 32; > > tsf_lo = ((u32) tsf) >> 10; > Why add this warning here if you already have the additions below? We > don't need multiple layers of defensive checks for the same thing. > > > @@ -667,6 +669,8 @@ static void ath9k_cache_beacon_config(struct ath_softc *sc, > > "Caching beacon data for BSS: %pM\n", bss_conf->bssid); > > > > cur_conf->beacon_interval = bss_conf->beacon_int; > > + if (WARN_ON_ONCE(cur_conf->beacon_interval == 0)) > > + cur_conf->beacon_interval = 100; > > cur_conf->dtim_period = bss_conf->dtim_period; > > cur_conf->listen_interval = 1; > > cur_conf->dtim_count = 1; > > diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c > > index b97217d..79c20c7 100644 > > --- a/drivers/net/wireless/ath/ath9k/recv.c > > +++ b/drivers/net/wireless/ath/ath9k/recv.c > > @@ -538,7 +538,8 @@ static void ath_rx_ps_beacon(struct ath_softc *sc, struct sk_buff *skb) > > sc->ps_flags &= ~PS_BEACON_SYNC; > > ath_dbg(common, PS, > > "Reconfigure beacon timers based on synchronized timestamp\n"); > > - ath9k_set_beacon(sc); > > + if (!(WARN_ON_ONCE(sc->cur_beacon_conf.beacon_interval == 0))) > > + ath9k_set_beacon(sc); > > } > > > > if (ath_beacon_dtim_pending_cab(skb)) { > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-wireless" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- John W. Linville Someday the world will need a hero, and you linville@tuxdriver.com might be all we have. Be ready.