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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: netdev@vger.kernel.org, tipc-discussion@lists.sourceforge.net, linux-kernel@vger.kernel.org, Xiang Mei , Weiming Shi Subject: [PATCH net v2] tipc: serialize udp bearer replicast list updates Date: Tue, 7 Jul 2026 09:42:49 -0700 Message-ID: <20260707164248.821265-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit tipc_udp_rcast_add() and cleanup_bearer() both update ub->rcast.list with list_add_rcu() / list_del_rcu(), but nothing serializes them. The add runs from the encap receive softirq (via tipc_udp_rcast_disc()) without rtnl_lock(), so it can race the cleanup delete and corrupt the list: list_del corruption. prev->next should be ffff8880298d7ab8, but was ffff88802449ad38. (prev=ffff888027e3ec98) kernel BUG at lib/list_debug.c:62! RIP: __list_del_entry_valid_or_report+0x17a/0x200 Workqueue: events cleanup_bearer Call Trace: cleanup_bearer (net/tipc/udp_media.c:811) process_one_work (kernel/workqueue.c:3302) worker_thread (kernel/workqueue.c:3466) The bearer can be enabled from an unprivileged user namespace, as the TIPCv2 generic-netlink ops carry no GENL_ADMIN_PERM. Add a spinlock to struct udp_bearer and take it around the list_add_rcu() in tipc_udp_rcast_add() and the list_del_rcu() loop in cleanup_bearer() so the two writers can no longer corrupt the list. While here, switch the read-only walk in tipc_udp_is_known_peer() to list_for_each_entry_rcu(); it never deletes, so list_for_each_entry_safe() was misleading. Fixes: ef20cd4dd163 ("tipc: introduce UDP replicast") Reported-by: Xiang Mei Suggested-by: Tung Nguyen Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Weiming Shi --- v2: (per Tung's review) - Narrow the lock to just list_add_rcu(). - Drop the under-lock dup re-check; serializing the writers is enough. - Use list_for_each_entry_rcu() in tipc_udp_is_known_peer(). net/tipc/udp_media.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c index 62ae7f5b5840..c6aa8c3c54ce 100644 --- a/net/tipc/udp_media.c +++ b/net/tipc/udp_media.c @@ -94,6 +94,7 @@ struct udp_replicast { * @ifindex: local address scope * @work: used to schedule deferred work on a bearer * @rcast: associated udp_replicast container + * @rcast_lock: serializes updates to @rcast.list */ struct udp_bearer { struct tipc_bearer __rcu *bearer; @@ -101,6 +102,7 @@ struct udp_bearer { u32 ifindex; struct work_struct work; struct udp_replicast rcast; + spinlock_t rcast_lock; /* protects rcast.list */ }; static int tipc_udp_is_mcast_addr(struct udp_media_addr *addr) @@ -281,7 +283,7 @@ static int tipc_udp_send_msg(struct net *net, struct sk_buff *skb, static bool tipc_udp_is_known_peer(struct tipc_bearer *b, struct udp_media_addr *addr) { - struct udp_replicast *rcast, *tmp; + struct udp_replicast *rcast; struct udp_bearer *ub; ub = rcu_dereference_rtnl(b->media_ptr); @@ -290,7 +292,7 @@ static bool tipc_udp_is_known_peer(struct tipc_bearer *b, return false; } - list_for_each_entry_safe(rcast, tmp, &ub->rcast.list, list) { + list_for_each_entry_rcu(rcast, &ub->rcast.list, list) { if (!memcmp(&rcast->addr, addr, sizeof(struct udp_media_addr))) return true; } @@ -326,7 +328,9 @@ static int tipc_udp_rcast_add(struct tipc_bearer *b, pr_info("New replicast peer: %pI6\n", &rcast->addr.ipv6); #endif b->bcast_addr.broadcast = TIPC_REPLICAST_SUPPORT; + spin_lock_bh(&ub->rcast_lock); list_add_rcu(&rcast->list, &ub->rcast.list); + spin_unlock_bh(&ub->rcast_lock); return 0; } @@ -679,6 +683,7 @@ static int tipc_udp_enable(struct net *net, struct tipc_bearer *b, return -ENOMEM; INIT_LIST_HEAD(&ub->rcast.list); + spin_lock_init(&ub->rcast_lock); if (!attrs[TIPC_NLA_BEARER_UDP_OPTS]) goto err; @@ -819,10 +824,12 @@ static void cleanup_bearer(struct work_struct *work) struct udp_replicast *rcast, *tmp; struct tipc_net *tn; + spin_lock_bh(&ub->rcast_lock); list_for_each_entry_safe(rcast, tmp, &ub->rcast.list, list) { list_del_rcu(&rcast->list); call_rcu_hurry(&rcast->rcu, rcast_free_rcu); } + spin_unlock_bh(&ub->rcast_lock); tn = tipc_net(sock_net(ub->sk)); -- 2.43.0