[IPV6] ADDRCONF: Allow longer lifetime on 64bit archs.

- Allow longer lifetimes (>= 0x7fffffff/HZ) on 64bit archs
  by using unsigned long.
- Shadow this arithmetic overflow workaround by introducing
  helper functions: addrconf_timeout_fixup() and
  addrconf_finite_timeout().

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

3 files changed, 75 insertions, 56 deletions

diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 0a2f037..bbd3d58 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -94,6 +94,28 @@ extern void			addrconf_join_solict(struct net_device *dev,
 extern void			addrconf_leave_solict(struct inet6_dev *idev,
 					struct in6_addr *addr);
 
+static inline unsigned long addrconf_timeout_fixup(u32 timeout,
+						    unsigned unit)
+{
+	if (timeout == 0xffffffff)
+		return ~0UL;
+
+	/*
+	 * Avoid arithmetic overflow.
+	 * Assuming unit is constant and non-zero, this "if" statement
+	 * will go away on 64bit archs.
+	 */
+	if (0xfffffffe > LONG_MAX / unit && timeout > LONG_MAX / unit)
+		return LONG_MAX / unit;
+
+	return timeout;
+}
+
+static inline int addrconf_finite_timeout(unsigned long timeout)
+{
+	return ~timeout;
+}
+
 /*
  *	IPv6 Address Label subsystem (addrlabel.c)
  */
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index c3b20c5..147588f 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -731,8 +731,13 @@ static void ipv6_del_addr(struct inet6_ifaddr *ifp)
 						onlink = -1;
 
 					spin_lock(&ifa->lock);
-					lifetime = min_t(unsigned long,
-							 ifa->valid_lft, 0x7fffffffUL/HZ);
+
+					lifetime = addrconf_timeout_fixup(ifa->valid_lft, HZ);
+					/*
+					 * Note: Because this address is
+					 * not permanent, lifetime <
+					 * LONG_MAX / HZ here.
+					 */
 					if (time_before(expires,
 							ifa->tstamp + lifetime * HZ))
 						expires = ifa->tstamp + lifetime * HZ;
@@ -1722,7 +1727,6 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len)
 	__u32 valid_lft;
 	__u32 prefered_lft;
 	int addr_type;
-	unsigned long rt_expires;
 	struct inet6_dev *in6_dev;
 
 	pinfo = (struct prefix_info *) opt;
@@ -1764,28 +1768,23 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len)
 	 *	2) Configure prefixes with the auto flag set
 	 */
 
-	if (valid_lft == INFINITY_LIFE_TIME)
-		rt_expires = ~0UL;
-	else if (valid_lft >= 0x7FFFFFFF/HZ) {
+	if (pinfo->onlink) {
+		struct rt6_info *rt;
+		unsigned long rt_expires;
+
 		/* Avoid arithmetic overflow. Really, we could
 		 * save rt_expires in seconds, likely valid_lft,
 		 * but it would require division in fib gc, that it
 		 * not good.
 		 */
-		rt_expires = 0x7FFFFFFF - (0x7FFFFFFF % HZ);
-	} else
-		rt_expires = valid_lft * HZ;
+		if (HZ > USER_HZ)
+			rt_expires = addrconf_timeout_fixup(valid_lft, HZ);
+		else
+			rt_expires = addrconf_timeout_fixup(valid_lft, USER_HZ);
 
-	/*
-	 * We convert this (in jiffies) to clock_t later.
-	 * Avoid arithmetic overflow there as well.
-	 * Overflow can happen only if HZ < USER_HZ.
-	 */
-	if (HZ < USER_HZ && ~rt_expires && rt_expires > 0x7FFFFFFF / USER_HZ)
-		rt_expires = 0x7FFFFFFF / USER_HZ;
+		if (addrconf_finite_timeout(rt_expires))
+			rt_expires *= HZ;
 
-	if (pinfo->onlink) {
-		struct rt6_info *rt;
 		rt = rt6_lookup(dev_net(dev), &pinfo->prefix, NULL,
 				dev->ifindex, 1);
 
@@ -1794,7 +1793,7 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len)
 			if (valid_lft == 0) {
 				ip6_del_rt(rt);
 				rt = NULL;
-			} else if (~rt_expires) {
+			} else if (addrconf_finite_timeout(rt_expires)) {
 				/* not infinity */
 				rt->rt6i_expires = jiffies + rt_expires;
 				rt->rt6i_flags |= RTF_EXPIRES;
@@ -1803,9 +1802,9 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len)
 				rt->rt6i_expires = 0;
 			}
 		} else if (valid_lft) {
-			int flags = RTF_ADDRCONF | RTF_PREFIX_RT;
 			clock_t expires = 0;
-			if (~rt_expires) {
+			int flags = RTF_ADDRCONF | RTF_PREFIX_RT;
+			if (addrconf_finite_timeout(rt_expires)) {
 				/* not infinity */
 				flags |= RTF_EXPIRES;
 				expires = jiffies_to_clock_t(rt_expires);
@@ -2036,6 +2035,7 @@ static int inet6_addr_add(struct net *net, int ifindex, struct in6_addr *pfx,
 	int scope;
 	u32 flags;
 	clock_t expires;
+	unsigned long timeout;
 
 	ASSERT_RTNL();
 
@@ -2055,22 +2055,23 @@ static int inet6_addr_add(struct net *net, int ifindex, struct in6_addr *pfx,
 
 	scope = ipv6_addr_scope(pfx);
 
-	if (valid_lft == INFINITY_LIFE_TIME) {
-		ifa_flags |= IFA_F_PERMANENT;
-		flags = 0;
-		expires = 0;
-	} else {
-		if (valid_lft >= 0x7FFFFFFF/HZ)
-			valid_lft = 0x7FFFFFFF/HZ;
+	timeout = addrconf_timeout_fixup(valid_lft, HZ);
+	if (addrconf_finite_timeout(timeout)) {
+		expires = jiffies_to_clock_t(timeout * HZ);
+		valid_lft = timeout;
 		flags = RTF_EXPIRES;
-		expires = jiffies_to_clock_t(valid_lft * HZ);
+	} else {
+		expires = 0;
+		flags = 0;
+		ifa_flags |= IFA_F_PERMANENT;
 	}
 
-	if (prefered_lft == 0)
-		ifa_flags |= IFA_F_DEPRECATED;
-	else if ((prefered_lft >= 0x7FFFFFFF/HZ) &&
-		 (prefered_lft != INFINITY_LIFE_TIME))
-		prefered_lft = 0x7FFFFFFF/HZ;
+	timeout = addrconf_timeout_fixup(prefered_lft, HZ);
+	if (addrconf_finite_timeout(timeout)) {
+		if (timeout == 0)
+			ifa_flags |= IFA_F_DEPRECATED;
+		prefered_lft = timeout;
+	}
 
 	ifp = ipv6_add_addr(idev, pfx, plen, scope, ifa_flags);
 
@@ -3175,26 +3176,28 @@ static int inet6_addr_modify(struct inet6_ifaddr *ifp, u8 ifa_flags,
 {
 	u32 flags;
 	clock_t expires;
+	unsigned long timeout;
 
 	if (!valid_lft || (prefered_lft > valid_lft))
 		return -EINVAL;
 
-	if (valid_lft == INFINITY_LIFE_TIME) {
-		ifa_flags |= IFA_F_PERMANENT;
-		flags = 0;
-		expires = 0;
-	} else {
-		if (valid_lft >= 0x7FFFFFFF/HZ)
-			valid_lft = 0x7FFFFFFF/HZ;
+	timeout = addrconf_timeout_fixup(valid_lft, HZ);
+	if (addrconf_finite_timeout(timeout)) {
+		expires = jiffies_to_clock_t(timeout * HZ);
+		valid_lft = timeout;
 		flags = RTF_EXPIRES;
-		expires = jiffies_to_clock_t(valid_lft * HZ);
+	} else {
+		expires = 0;
+		flags = 0;
+		ifa_flags |= IFA_F_PERMANENT;
 	}
 
-	if (prefered_lft == 0)
-		ifa_flags |= IFA_F_DEPRECATED;
-	else if ((prefered_lft >= 0x7FFFFFFF/HZ) &&
-		 (prefered_lft != INFINITY_LIFE_TIME))
-		prefered_lft = 0x7FFFFFFF/HZ;
+	timeout = addrconf_timeout_fixup(prefered_lft, HZ);
+	if (addrconf_finite_timeout(timeout)) {
+		if (timeout == 0)
+			ifa_flags |= IFA_F_DEPRECATED;
+		prefered_lft = timeout;
+	}
 
 	spin_lock_bh(&ifp->lock);
 	ifp->flags = (ifp->flags & ~(IFA_F_DEPRECATED | IFA_F_PERMANENT | IFA_F_NODAD | IFA_F_HOMEADDRESS)) | ifa_flags;
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 48534c6..220cffe 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -446,7 +446,7 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
 	struct route_info *rinfo = (struct route_info *) opt;
 	struct in6_addr prefix_buf, *prefix;
 	unsigned int pref;
-	u32 lifetime;
+	unsigned long lifetime;
 	struct rt6_info *rt;
 
 	if (len < sizeof(struct route_info)) {
@@ -472,13 +472,7 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
 	if (pref == ICMPV6_ROUTER_PREF_INVALID)
 		pref = ICMPV6_ROUTER_PREF_MEDIUM;
 
-	lifetime = ntohl(rinfo->lifetime);
-	if (lifetime == 0xffffffff) {
-		/* infinity */
-	} else if (lifetime > 0x7fffffff/HZ - 1) {
-		/* Avoid arithmetic overflow */
-		lifetime = 0x7fffffff/HZ - 1;
-	}
+	lifetime = addrconf_timeout_fixup(ntohl(rinfo->lifetime), HZ);
 
 	if (rinfo->length == 3)
 		prefix = (struct in6_addr *)rinfo->prefix;
@@ -506,7 +500,7 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
 				 (rt->rt6i_flags & ~RTF_PREF_MASK) | RTF_PREF(pref);
 
 	if (rt) {
-		if (lifetime == 0xffffffff) {
+		if (!addrconf_finite_timeout(lifetime)) {
 			rt->rt6i_flags &= ~RTF_EXPIRES;
 		} else {
 			rt->rt6i_expires = jiffies + HZ * lifetime;