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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Daehyeon Ko <4ncienth@gmail.com> Subject: [PATCH net v3 1/3] ipv6: serialize address publication with device teardown Date: Fri, 9 Oct 2026 14:40:40 +0900 Message-ID: <20261009054042.272944-2-4ncienth@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261009054042.272944-1-4ncienth@gmail.com> References: <20261009054042.272944-1-4ncienth@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ipv6_add_addr() checks idev state before allocating an ifaddr, but publishes the object later. addrconf_ifdown() can mark and detach the idev between the check and publication. This happens when a non-loopback device MTU falls below IPV6_MIN_MTU. A forced interleaving published an address on a dead idev, and later device deletion waited indefinitely for the leaked references. Protect the dead indication with idev->lock and keep that lock across both hash and device-list publication. Use READ_ONCE() for the initial lockless state checks, then recheck both dead and disable_ipv6 before publishing. If teardown wins, reject the unpublished object. Fixes: 8814c4b53381 ("[IPV6] ADDRCONF: Convert addrconf_lock to RCU.") Cc: stable@vger.kernel.org Suggested-by: Ido Schimmel Assisted-by: LLM Signed-off-by: Daehyeon Ko <4ncienth@gmail.com> --- net/ipv6/addrconf.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index c90ee6dd7446cd..77b3b1154d591c 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -1095,13 +1095,13 @@ ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config *cfg, return ERR_PTR(-EADDRNOTAVAIL); } - if (idev->dead) { + if (READ_ONCE(idev->dead)) { NL_SET_ERR_MSG_MOD(extack, "device is going away"); err = -ENODEV; goto out; } - if (idev->cnf.disable_ipv6) { + if (READ_ONCE(idev->cnf.disable_ipv6)) { NL_SET_ERR_MSG_MOD(extack, "IPv6 is disabled on this device"); err = -EACCES; goto out; @@ -1168,14 +1168,20 @@ ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config *cfg, rcu_read_lock(); - err = ipv6_add_addr_hash(idev->dev, ifa); + write_lock_bh(&idev->lock); + + if (idev->dead) + err = -ENODEV; + else if (READ_ONCE(idev->cnf.disable_ipv6)) + err = -EACCES; + else + err = ipv6_add_addr_hash(idev->dev, ifa); if (err < 0) { + write_unlock_bh(&idev->lock); rcu_read_unlock(); goto out; } - write_lock_bh(&idev->lock); - /* Add to inet6_dev unicast addr list. */ ipv6_link_dev_addr(idev, ifa); @@ -3897,7 +3903,9 @@ static int addrconf_ifdown(struct net_device *dev, bool unregister) * Do not dev_put! */ if (unregister) { + write_lock_bh(&idev->lock); WRITE_ONCE(idev->dead, 1); + write_unlock_bh(&idev->lock); /* protected by rtnl_lock */ RCU_INIT_POINTER(dev->ip6_ptr, NULL); -- 2.55.0