From: Weiming Shi Date: Thu, 16 Jul 2026 02:52:04 +0000 (-0700) Subject: tipc: serialize udp bearer replicast list updates X-Git-Tag: v7.2-rc5~27^2~87 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=350e592ff4e30e48ffb55e142d11a73e63f4869c;p=thirdparty%2Fkernel%2Flinux.git tipc: serialize udp bearer replicast list updates 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. Reject a duplicate peer under the same lock before allocating, and remove tipc_udp_is_known_peer(). The old lockless pre-check in tipc_udp_rcast_disc() was racy: two softirqs discovering the same peer could both find it absent and add it twice. cleanup_bearer() runs from a workqueue after tipc_udp_disable() clears the bearer's up bit, so an encap softirq can still reach tipc_udp_rcast_add() and add a peer after cleanup_bearer() has already emptied the list, leaking that entry when the bearer is freed. Mark the bearer disabled under rcast_lock once the list is emptied and refuse further additions. Fixes: ef20cd4dd163 ("tipc: introduce UDP replicast") Reported-by: Xiang Mei Suggested-by: Tung Nguyen Signed-off-by: Weiming Shi Reviewed-by: Tung Nguyen Link: https://patch.msgid.link/20260716025203.9332-2-bestswngs@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c index 62ae7f5b5840..230645cc01c9 100644 --- a/net/tipc/udp_media.c +++ b/net/tipc/udp_media.c @@ -94,6 +94,8 @@ struct udp_replicast { * @ifindex: local address scope * @work: used to schedule deferred work on a bearer * @rcast: associated udp_replicast container + * @rcast_lock: serialize updates to @rcast.list against concurrent updaters + * @disabled: bearer is being torn down; reject further @rcast.list additions */ struct udp_bearer { struct tipc_bearer __rcu *bearer; @@ -101,6 +103,8 @@ struct udp_bearer { u32 ifindex; struct work_struct work; struct udp_replicast rcast; + spinlock_t rcast_lock; + bool disabled; }; static int tipc_udp_is_mcast_addr(struct udp_media_addr *addr) @@ -278,26 +282,6 @@ out: return err; } -static bool tipc_udp_is_known_peer(struct tipc_bearer *b, - struct udp_media_addr *addr) -{ - struct udp_replicast *rcast, *tmp; - struct udp_bearer *ub; - - ub = rcu_dereference_rtnl(b->media_ptr); - if (!ub) { - pr_err_ratelimited("UDP bearer instance not found\n"); - return false; - } - - list_for_each_entry_safe(rcast, tmp, &ub->rcast.list, list) { - if (!memcmp(&rcast->addr, addr, sizeof(struct udp_media_addr))) - return true; - } - - return false; -} - static int tipc_udp_rcast_add(struct tipc_bearer *b, struct udp_media_addr *addr) { @@ -308,16 +292,34 @@ static int tipc_udp_rcast_add(struct tipc_bearer *b, if (!ub) return -ENODEV; + spin_lock_bh(&ub->rcast_lock); + if (ub->disabled) { + spin_unlock_bh(&ub->rcast_lock); + return 0; + } + list_for_each_entry(rcast, &ub->rcast.list, list) { + if (!memcmp(&rcast->addr, addr, sizeof(*addr))) { + spin_unlock_bh(&ub->rcast_lock); + return 0; + } + } + rcast = kmalloc_obj(*rcast, GFP_ATOMIC); - if (!rcast) + if (!rcast) { + spin_unlock_bh(&ub->rcast_lock); return -ENOMEM; + } if (dst_cache_init(&rcast->dst_cache, GFP_ATOMIC)) { + spin_unlock_bh(&ub->rcast_lock); kfree(rcast); return -ENOMEM; } memcpy(&rcast->addr, addr, sizeof(struct udp_media_addr)); + list_add_rcu(&rcast->list, &ub->rcast.list); + b->bcast_addr.broadcast = TIPC_REPLICAST_SUPPORT; + spin_unlock_bh(&ub->rcast_lock); if (ntohs(addr->proto) == ETH_P_IP) pr_info("New replicast peer: %pI4\n", &rcast->addr.ipv4); @@ -325,8 +327,6 @@ static int tipc_udp_rcast_add(struct tipc_bearer *b, else if (ntohs(addr->proto) == ETH_P_IPV6) pr_info("New replicast peer: %pI6\n", &rcast->addr.ipv6); #endif - b->bcast_addr.broadcast = TIPC_REPLICAST_SUPPORT; - list_add_rcu(&rcast->list, &ub->rcast.list); return 0; } @@ -361,9 +361,6 @@ static int tipc_udp_rcast_disc(struct tipc_bearer *b, struct sk_buff *skb) return 0; } - if (likely(tipc_udp_is_known_peer(b, &src))) - return 0; - return tipc_udp_rcast_add(b, &src); } @@ -644,9 +641,6 @@ int tipc_udp_nl_bearer_add(struct tipc_bearer *b, struct nlattr *attr) return -EINVAL; } - if (tipc_udp_is_known_peer(b, &addr)) - return 0; - return tipc_udp_rcast_add(b, &addr); } @@ -679,6 +673,7 @@ 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 +814,13 @@ 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); } + ub->disabled = true; + spin_unlock_bh(&ub->rcast_lock); tn = tipc_net(sock_net(ub->sk));