bridge: don't allow setting hello time to zero

Dushan Tcholich reports that on his system ksoftirqd can consume
between %6 to %10 of cpu time, and cause ~200 context switches per
second.

He then correlated this with a report by bdupree@techfinesse.com:

	http://marc.info/?l=linux-kernel&m=119613299024398&w=2

and the culprit cause seems to be starting the bridge interface.
In particular, when starting the bridge interface, his scripts
are specifying a hello timer interval of "0".

The bridge hello time can't be safely set to values less than 1
second, otherwise it is possible to end up with a runaway timer.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index eeee218..5bbf073 100644 (file)
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -188,15 +188,21 @@ static int old_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
                return 0;
 
        case BRCTL_SET_BRIDGE_HELLO_TIME:
+       {
+               unsigned long t = clock_t_to_jiffies(args[1]);
                if (!capable(CAP_NET_ADMIN))
                        return -EPERM;
 
+               if (t < HZ)
+                       return -EINVAL;
+
                spin_lock_bh(&br->lock);
-               br->bridge_hello_time = clock_t_to_jiffies(args[1]);
+               br->bridge_hello_time = t;
                if (br_is_root_bridge(br))
                        br->hello_time = br->bridge_hello_time;
                spin_unlock_bh(&br->lock);
                return 0;
+       }
 
        case BRCTL_SET_BRIDGE_MAX_AGE:
                if (!capable(CAP_NET_ADMIN))

diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
index 27d6a51..158dee8 100644 (file)
--- a/net/bridge/br_sysfs_br.c
+++ b/net/bridge/br_sysfs_br.c
@@ -29,11 +29,12 @@
  */
 static ssize_t store_bridge_parm(struct device *d,
                                 const char *buf, size_t len,
-                                void (*set)(struct net_bridge *, unsigned long))
+                                int (*set)(struct net_bridge *, unsigned long))
 {
        struct net_bridge *br = to_bridge(d);
        char *endp;
        unsigned long val;
+       int err;
 
        if (!capable(CAP_NET_ADMIN))
                return -EPERM;
@@ -43,9 +44,9 @@ static ssize_t store_bridge_parm(struct device *d,
                return -EINVAL;
 
        spin_lock_bh(&br->lock);
-       (*set)(br, val);
+       err = (*set)(br, val);
        spin_unlock_bh(&br->lock);
-       return len;
+       return err ? err : len;
 }
 
 
@@ -56,12 +57,13 @@ static ssize_t show_forward_delay(struct device *d,
        return sprintf(buf, "%lu\n", jiffies_to_clock_t(br->forward_delay));
 }
 
-static void set_forward_delay(struct net_bridge *br, unsigned long val)
+static int set_forward_delay(struct net_bridge *br, unsigned long val)
 {
        unsigned long delay = clock_t_to_jiffies(val);
        br->forward_delay = delay;
        if (br_is_root_bridge(br))
                br->bridge_forward_delay = delay;
+       return 0;
 }
 
 static ssize_t store_forward_delay(struct device *d,
@@ -80,12 +82,17 @@ static ssize_t show_hello_time(struct device *d, struct device_attribute *attr,
                       jiffies_to_clock_t(to_bridge(d)->hello_time));
 }
 
-static void set_hello_time(struct net_bridge *br, unsigned long val)
+static int set_hello_time(struct net_bridge *br, unsigned long val)
 {
        unsigned long t = clock_t_to_jiffies(val);
+
+       if (t < HZ)
+               return -EINVAL;
+
        br->hello_time = t;
        if (br_is_root_bridge(br))
                br->bridge_hello_time = t;
+       return 0;
 }
 
 static ssize_t store_hello_time(struct device *d,
@@ -104,12 +111,13 @@ static ssize_t show_max_age(struct device *d, struct device_attribute *attr,
                       jiffies_to_clock_t(to_bridge(d)->max_age));
 }
 
-static void set_max_age(struct net_bridge *br, unsigned long val)
+static int set_max_age(struct net_bridge *br, unsigned long val)
 {
        unsigned long t = clock_t_to_jiffies(val);
        br->max_age = t;
        if (br_is_root_bridge(br))
                br->bridge_max_age = t;
+       return 0;
 }
 
 static ssize_t store_max_age(struct device *d, struct device_attribute *attr,
@@ -126,9 +134,10 @@ static ssize_t show_ageing_time(struct device *d,
        return sprintf(buf, "%lu\n", jiffies_to_clock_t(br->ageing_time));
 }
 
-static void set_ageing_time(struct net_bridge *br, unsigned long val)
+static int set_ageing_time(struct net_bridge *br, unsigned long val)
 {
        br->ageing_time = clock_t_to_jiffies(val);
+       return 0;
 }
 
 static ssize_t store_ageing_time(struct device *d,
@@ -180,9 +189,10 @@ static ssize_t show_priority(struct device *d, struct device_attribute *attr,
                       (br->bridge_id.prio[0] << 8) | br->bridge_id.prio[1]);
 }
 
-static void set_priority(struct net_bridge *br, unsigned long val)
+static int set_priority(struct net_bridge *br, unsigned long val)
 {
        br_stp_set_bridge_priority(br, (u16) val);
+       return 0;
 }
 
 static ssize_t store_priority(struct device *d, struct device_attribute *attr,