netdev - [PATCH] bridge: don't allow setting hello time to zero

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Date:	Thu, 4 Sep 2008 15:47:09 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	David Miller <davem@...emloft.net>
Cc:	"Dushan Tcholich" <dusanc@...il.com>,
	"Francois Romieu" <romieu@...zoreil.com>,
	"Robert Hancock" <hancockr@...w.ca>, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	bridge@...ts.linux-foundation.org
Subject: [PATCH] bridge: don't allow setting hello time to zero

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@...tta.com>

--- a/net/bridge/br_ioctl.c	2008-09-04 15:25:41.000000000 -0700
+++ b/net/bridge/br_ioctl.c	2008-09-04 15:44:33.000000000 -0700
@@ -188,15 +188,21 @@ static int old_dev_ioctl(struct net_devi
 		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))
--- a/net/bridge/br_sysfs_br.c	2008-09-04 15:27:20.000000000 -0700
+++ b/net/bridge/br_sysfs_br.c	2008-09-04 15:33:31.000000000 -0700
@@ -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 
 		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
 	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 de
 		       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 devic
 		       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 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 devi
 		       (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,

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