[PATCH 5.4 25/43] ipv6: prevent a possible race condition with lifetimes

[Greg Kroah-Hartman]

From: Niels Dossche <dossche.niels@xxxxxxxxx>

[ Upstream commit 6c0d8833a605e195ae219b5042577ce52bf71fff ]

valid_lft, prefered_lft and tstamp are always accessed under the lock
"lock" in other places. Reading these without taking the lock may result
in inconsistencies regarding the calculation of the valid and preferred
variables since decisions are taken on these fields for those variables.

Signed-off-by: Niels Dossche <dossche.niels@xxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
Signed-off-by: Niels Dossche <niels.dossche@xxxxxxxx>
Link: https://lore.kernel.org/r/20220223131954.6570-1-niels.dossche@xxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/ipv6/addrconf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index d1f29a3eb70b..60d070b25484 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4924,6 +4924,7 @@ static int inet6_fill_ifaddr(struct sk_buff *skb, struct inet6_ifaddr *ifa,
 	    nla_put_s32(skb, IFA_TARGET_NETNSID, args->netnsid))
 		goto error;
 
+	spin_lock_bh(&ifa->lock);
 	if (!((ifa->flags&IFA_F_PERMANENT) &&
 	      (ifa->prefered_lft == INFINITY_LIFE_TIME))) {
 		preferred = ifa->prefered_lft;
@@ -4945,6 +4946,7 @@ static int inet6_fill_ifaddr(struct sk_buff *skb, struct inet6_ifaddr *ifa,
 		preferred = INFINITY_LIFE_TIME;
 		valid = INFINITY_LIFE_TIME;
 	}
+	spin_unlock_bh(&ifa->lock);
 
 	if (!ipv6_addr_any(&ifa->peer_addr)) {
 		if (nla_put_in6_addr(skb, IFA_LOCAL, &ifa->addr) < 0 ||
-- 
2.34.1