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[129.161.139.80]) by smtp.gmail.com with ESMTPSA id p53sm2775779qtk.23.2019.09.27.08.41.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Sep 2019 08:41:03 -0700 (PDT) Date: Fri, 27 Sep 2019 11:41:02 -0400 From: Aaron Hill To: linux-wireless@vger.kernel.org Cc: Johannes Berg , "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] net: mac80211: Disable preeemption when updating stat counters Message-ID: <20190927154102.GA117350@ArchLaptop> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.12.2 (2019-09-21) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The mac80211 subsystem maintains per-cpu stat counters for receive and transmit operations. Previously, preemption was not disabled when updating these counters. This creates a race condition where two cpus could attempt to update the same counters using non-atomic operations. This was causing a 'BUG: using smp_processor_id() in preemptible [00000000] code' message to be printed, along with a stacktrace. This was reported in a few different places: * https://www.spinics.net/lists/linux-wireless/msg189992.html * https://bugzilla.kernel.org/show_bug.cgi?id=204127 This patch adds calls to preempt_disable() and preempt_enable() surrounding the updating of the stat counters. Signed-off-by: Aaron Hill --- net/mac80211/rx.c | 7 ++++++- net/mac80211/tx.c | 7 ++++++- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c index 768d14c9a716..5ef0667151bf 100644 --- a/net/mac80211/rx.c +++ b/net/mac80211/rx.c @@ -34,12 +34,17 @@ static inline void ieee80211_rx_stats(struct net_device *dev, u32 len) { - struct pcpu_sw_netstats *tstats = this_cpu_ptr(dev->tstats); + struct pcpu_sw_netstats *tstats; + + // Disable preemption while updating per-cpu stats counters + preempt_disable(); + tstats = this_cpu_ptr(dev->tstats); u64_stats_update_begin(&tstats->syncp); tstats->rx_packets++; tstats->rx_bytes += len; u64_stats_update_end(&tstats->syncp); + preempt_enable(); } static u8 *ieee80211_get_bssid(struct ieee80211_hdr *hdr, size_t len, diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index 1fa422782905..4cad3d741b6b 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -40,12 +40,17 @@ static inline void ieee80211_tx_stats(struct net_device *dev, u32 len) { - struct pcpu_sw_netstats *tstats = this_cpu_ptr(dev->tstats); + struct pcpu_sw_netstats *tstats; + + // Disable preemption while updating per-cpu stats counters + preempt_disable(); + tstats = this_cpu_ptr(dev->tstats); u64_stats_update_begin(&tstats->syncp); tstats->tx_packets++; tstats->tx_bytes += len; u64_stats_update_end(&tstats->syncp); + preempt_enable(); } static __le16 ieee80211_duration(struct ieee80211_tx_data *tx,