From 44075f563793880d17d1a2f3a17e06835b157d07 Mon Sep 17 00:00:00 2001 From: Ido Schimmel Date: Sun, 11 Aug 2019 10:35:48 +0300 Subject: [PATCH] drop_monitor: Reset per-CPU data before starting to trace The function reset_per_cpu_data() allocates and prepares a new skb for the summary netlink alert message ('NET_DM_CMD_ALERT'). The new skb is stored in the per-CPU 'data' variable and the old is returned. The function is invoked during module initialization and from the workqueue, before an alert is sent. This means that it is possible to receive an alert with stale data, if we stopped tracing when the hysteresis timer ('data->send_timer') was pending. Instead of invoking the function during module initialization, invoke it just before we start tracing and ensure we get a fresh skb. This also allows us to remove the calls to initialize the timer and the work item from the module initialization path, since both could have been triggered by the error paths of reset_per_cpu_data(). Signed-off-by: Ido Schimmel Signed-off-by: David S. Miller --- net/core/drop_monitor.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c index b266dc1660ed..1cf4988de591 100644 --- a/net/core/drop_monitor.c +++ b/net/core/drop_monitor.c @@ -252,9 +252,16 @@ static int net_dm_trace_on_set(struct netlink_ext_ack *extack) for_each_possible_cpu(cpu) { struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu); + struct sk_buff *skb; INIT_WORK(&data->dm_alert_work, send_dm_alert); timer_setup(&data->send_timer, sched_send_work, 0); + /* Allocate a new per-CPU skb for the summary alert message and + * free the old one which might contain stale data from + * previous tracing. + */ + skb = reset_per_cpu_data(data); + consume_skb(skb); } rc = register_trace_kfree_skb(trace_kfree_skb_hit, NULL); @@ -475,10 +482,7 @@ static int __init init_net_drop_monitor(void) for_each_possible_cpu(cpu) { data = &per_cpu(dm_cpu_data, cpu); - INIT_WORK(&data->dm_alert_work, send_dm_alert); - timer_setup(&data->send_timer, sched_send_work, 0); spin_lock_init(&data->lock); - reset_per_cpu_data(data); } goto out; -- 2.11.0