netdev - [PATCH net-next 2/6] inet: annotate data-races around ifa->ifa_valid

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Date: Thu, 29 Feb 2024 11:40:12 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Jiri Pirko <jiri@...dia.com>, David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, 
	Florian Westphal <fw@...len.de>, eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 2/6] inet: annotate data-races around ifa->ifa_valid_lft

ifa->ifa_valid_lft can be read locklessly.

Add appropriate READ_ONCE()/WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/devinet.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 1316046d5f28955376091d9e02ab4594e19fbd09..99f3e7c57d36ff028edadd4efd66d996ddc5d9b4 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -714,26 +714,26 @@ 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 valid_lft;
 
 			if (ifa->ifa_flags & IFA_F_PERMANENT)
 				continue;
 
+			valid_lft = READ_ONCE(ifa->ifa_valid_lft);
 			tstamp = READ_ONCE(ifa->ifa_tstamp);
 			/* We try to batch several events at once. */
 			age = (now - tstamp +
 			       ADDRCONF_TIMER_FUZZ_MINUS) / HZ;
 
-			if (ifa->ifa_valid_lft != INFINITY_LIFE_TIME &&
-			    age >= ifa->ifa_valid_lft) {
+			if (valid_lft != INFINITY_LIFE_TIME &&
+			    age >= valid_lft) {
 				change_needed = true;
 			} else if (ifa->ifa_preferred_lft ==
 				   INFINITY_LIFE_TIME) {
 				continue;
 			} else if (age >= ifa->ifa_preferred_lft) {
-				if (time_before(tstamp +
-						ifa->ifa_valid_lft * HZ, next))
-					next = tstamp +
-					       ifa->ifa_valid_lft * HZ;
+				if (time_before(tstamp + valid_lft * HZ, next))
+					next = tstamp + valid_lft * HZ;
 
 				if (!(ifa->ifa_flags & IFA_F_DEPRECATED))
 					change_needed = true;
@@ -810,7 +810,7 @@ static void set_ifa_lifetime(struct in_ifaddr *ifa, __u32 valid_lft,
 
 	timeout = addrconf_timeout_fixup(valid_lft, HZ);
 	if (addrconf_finite_timeout(timeout))
-		ifa->ifa_valid_lft = timeout;
+		WRITE_ONCE(ifa->ifa_valid_lft, timeout);
 	else
 		ifa->ifa_flags |= IFA_F_PERMANENT;
 
@@ -1699,7 +1699,7 @@ 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;
-		valid = ifa->ifa_valid_lft;
+		valid = READ_ONCE(ifa->ifa_valid_lft);
 		if (preferred != INFINITY_LIFE_TIME) {
 			long tval = (jiffies - tstamp) / HZ;
 
-- 
2.44.0.278.ge034bb2e1d-goog