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Tue, 5 May 2026 22:28:26 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id jEjhEApv+mkbWgAAD6G6ig (envelope-from ); Tue, 05 May 2026 22:28:26 +0000 From: Fernando Fernandez Mancera To: netdev@vger.kernel.org Cc: linux-kselftest@vger.kernel.org, horms@kernel.org, pabeni@redhat.com, kuba@kernel.org, edumazet@google.com, davem@davemloft.net, idosch@nvidia.com, dsahern@kernel.org, Fernando Fernandez Mancera , =?UTF-8?q?=C5=81ukasz=20Stelmach?= Subject: [PATCH 1/2 net v2] ipv6: addrconf: fix temp address generation after prefix deprecation Date: Wed, 6 May 2026 00:28:01 +0200 Message-ID: <20260505222802.4296-1-fmancera@suse.de> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Flag: NO X-Spam-Score: -3.30 X-Spamd-Result: default: False [-3.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_SEVEN(0.00)[11]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:mid] X-Spam-Level: When a router temporarily deprecates an IPv6 prefix (either by sending a Router Advertisement with Preferred Lifetime = 0 or by letting the lifetime expire) and later restores it, the kernel permanently loses its ability to generate temporary privacy addresses (RFC 8981) for that prefix. This happens because the address worker attempts to generate a replacement temporary address when the current one nears expiration. As the base prefix is deprecated already, the generation fails after marking the temporary address already having spawned a replacement (ifp->regen_count++). When the router eventually restores the prefix, the temporary address becomes active again. However, once it naturally expires, the address worker sees this temporary address already tried to generate one and skips the regeneration. Fix this by verifying that the base prefix has sufficient preferred lifetime remaining before attempting to generate a new temporary address. In addition, make ipv6_create_tempaddr() return meaningful error codes. This way, we can catch if a 0-lft RA arrived just after we passed the verification mentioned above. If we don't have sufficient preferred lifetime remaining, the worker will keep the next timer as it is. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Łukasz Stelmach Closes: https://lore.kernel.org/netdev/87340td30q.fsf%25steelman@post.pl/ Signed-off-by: Fernando Fernandez Mancera --- v2: adjusted commit message, adjusted the implementation to cover all race conditions --- net/ipv6/addrconf.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 5476b6536eb7..23338747b429 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -1379,7 +1379,7 @@ static int ipv6_create_tempaddr(struct inet6_ifaddr *ifp, bool block) write_unlock_bh(&idev->lock); pr_info("%s: use_tempaddr is disabled\n", __func__); in6_dev_put(idev); - ret = -1; + ret = -EOPNOTSUPP; goto out; } spin_lock_bh(&ifp->lock); @@ -1390,7 +1390,7 @@ static int ipv6_create_tempaddr(struct inet6_ifaddr *ifp, bool block) pr_warn("%s: regeneration time exceeded - disabled temporary address support\n", __func__); in6_dev_put(idev); - ret = -1; + ret = -EADDRNOTAVAIL; goto out; } in6_ifa_hold(ifp); @@ -1466,7 +1466,7 @@ static int ipv6_create_tempaddr(struct inet6_ifaddr *ifp, bool block) cfg.preferred_lft > if_public_preferred_lft) { in6_ifa_put(ifp); in6_dev_put(idev); - ret = -1; + ret = -EINVAL; goto out; } } @@ -4655,8 +4655,17 @@ static void addrconf_verify_rtnl(struct net *net) /* This is a non-regenerated temporary addr. */ unsigned long regen_advance = ipv6_get_regen_advance(ifp->idev); + unsigned long pub_tstamp = READ_ONCE(ifp->ifpub->tstamp); + unsigned long pub_age = 0; + bool pub_expired = false; + + if (time_after(now, pub_tstamp)) + pub_age = (now - pub_tstamp) / HZ; - if (age + regen_advance >= ifp->prefered_lft) { + if (pub_age + regen_advance >= READ_ONCE(ifp->ifpub->prefered_lft)) + pub_expired = true; + + if (age + regen_advance >= ifp->prefered_lft && !pub_expired) { struct inet6_ifaddr *ifpub = ifp->ifpub; if (time_before(ifp->tstamp + ifp->prefered_lft * HZ, next)) next = ifp->tstamp + ifp->prefered_lft * HZ; @@ -4670,12 +4679,18 @@ static void addrconf_verify_rtnl(struct net *net) ifpub->regen_count = 0; spin_unlock(&ifpub->lock); rcu_read_unlock_bh(); - ipv6_create_tempaddr(ifpub, true); + + if (ipv6_create_tempaddr(ifpub, true) == -EINVAL) { + spin_lock_bh(&ifp->lock); + ifp->regen_count = 0; + spin_unlock_bh(&ifp->lock); + } in6_ifa_put(ifpub); in6_ifa_put(ifp); rcu_read_lock_bh(); goto restart; - } else if (time_before(ifp->tstamp + ifp->prefered_lft * HZ - regen_advance * HZ, next)) + } else if (time_before(ifp->tstamp + ifp->prefered_lft * HZ - regen_advance * HZ, next) && + !pub_expired) next = ifp->tstamp + ifp->prefered_lft * HZ - regen_advance * HZ; } -- 2.53.0