inet: annotate data-races around ifa->ifa_preferred_lft

ifa->ifa_preferred_lft can be read locklessly.

Add appropriate READ_ONCE()/WRITE_ONCE() annotations.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/devinet.c

@@ -714,11 +714,13 @@ static void check_lifetime(struct work_struct *work)
 		rcu_read_lock();
 		hlist_for_each_entry_rcu(ifa, &inet_addr_lst[i], hash) {
 			unsigned long age, tstamp;
+			u32 preferred_lft;
 			u32 valid_lft;
 
 			if (ifa->ifa_flags & IFA_F_PERMANENT)
 				continue;
 
+			preferred_lft = READ_ONCE(ifa->ifa_preferred_lft);
 			valid_lft = READ_ONCE(ifa->ifa_valid_lft);
 			tstamp = READ_ONCE(ifa->ifa_tstamp);
 			/* We try to batch several events at once. */
@@ -728,20 +730,18 @@ static void check_lifetime(struct work_struct *work)
 			if (valid_lft != INFINITY_LIFE_TIME &&
 			    age >= valid_lft) {
 				change_needed = true;
-			} else if (ifa->ifa_preferred_lft ==
+			} else if (preferred_lft ==
 				   INFINITY_LIFE_TIME) {
 				continue;
-			} else if (age >= ifa->ifa_preferred_lft) {
+			} else if (age >= preferred_lft) {
 				if (time_before(tstamp + valid_lft * HZ, next))
 					next = tstamp + valid_lft * HZ;
 
 				if (!(ifa->ifa_flags & IFA_F_DEPRECATED))
 					change_needed = true;
-			} else if (time_before(tstamp +
-					       ifa->ifa_preferred_lft * HZ,
+			} else if (time_before(tstamp + preferred_lft * HZ,
 					       next)) {
-				next = tstamp +
-				       ifa->ifa_preferred_lft * HZ;
+				next = tstamp + preferred_lft * HZ;
 			}
 		}
 		rcu_read_unlock();
@@ -818,7 +818,7 @@ static void set_ifa_lifetime(struct in_ifaddr *ifa, __u32 valid_lft,
 	if (addrconf_finite_timeout(timeout)) {
 		if (timeout == 0)
 			ifa->ifa_flags |= IFA_F_DEPRECATED;
-		ifa->ifa_preferred_lft = timeout;
+		WRITE_ONCE(ifa->ifa_preferred_lft, timeout);
 	}
 	WRITE_ONCE(ifa->ifa_tstamp, jiffies);
 	if (!ifa->ifa_cstamp)
@@ -1698,7 +1698,7 @@ static int inet_fill_ifaddr(struct sk_buff *skb, struct in_ifaddr *ifa,
 
 	tstamp = READ_ONCE(ifa->ifa_tstamp);
 	if (!(ifm->ifa_flags & IFA_F_PERMANENT)) {
-		preferred = ifa->ifa_preferred_lft;
+		preferred = READ_ONCE(ifa->ifa_preferred_lft);
 		valid = READ_ONCE(ifa->ifa_valid_lft);
 		if (preferred != INFINITY_LIFE_TIME) {
 			long tval = (jiffies - tstamp) / HZ;