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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Hoang Huu Le , Xiang Mei , linux-kernel@vger.kernel.org, Weiming Shi Subject: [PATCH net] tipc: fix NULL deref in tipc_named_node_up() on empty publication list Date: Sun, 5 Jul 2026 04:59:58 -0700 Message-ID: <20260705115958.1066751-1-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit named_distribute() builds the bulk messages for @pls into @list and then dereferences the tail skb: hdr = buf_msg(skb_peek_tail(list)); msg_set_last_bulk(hdr); If @pls is empty no skb is enqueued, skb_peek_tail() returns NULL, and msg_set_last_bulk() writes through buf_msg(NULL). tipc_named_node_up() passes &nt->cluster_scope. With a node-id configuration the TIPC_NODE_STATE name is published by tipc_net_finalize() from a work item, which sets the node address before publishing the name. The node accepts links once the address is set, so a link that comes up before the publish runs named_distribute() on an empty cluster_scope: KASAN: null-ptr-deref in range [0x00000000000000d8-0x00000000000000df] RIP: 0010:tipc_named_node_up (net/tipc/name_distr.c:196) tipc_named_node_up (net/tipc/name_distr.c:196 net/tipc/name_distr.c:221) tipc_node_write_unlock (net/tipc/node.c:428) tipc_rcv (net/tipc/node.c:2185) tipc_udp_recv (net/tipc/udp_media.c:392) Kernel panic - not syncing: Fatal exception in interrupt TIPC genl ops use GENL_UNS_ADMIN_PERM, so an unprivileged user can reach this from a user+net namespace. Return early from named_distribute() when the list is empty, and skip tipc_node_xmit() for an empty chain. The empty chain would otherwise hit tipc_lxc_xmit() -> buf_msg(skb_peek(list)), the same zero-skb case fixed for tipc_link_xmit() in commit b77413446408 ("tipc: fix NULL deref in tipc_link_xmit()"). Fixes: cad2929dc432 ("tipc: update a binding service via broadcast") Reported-by: Xiang Mei Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Weiming Shi --- net/tipc/name_distr.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c index ba4f4906e13b..c04fea4650a5 100644 --- a/net/tipc/name_distr.c +++ b/net/tipc/name_distr.c @@ -192,7 +192,10 @@ static void named_distribute(struct net *net, struct sk_buff_head *list, skb_trim(skb, INT_H_SIZE + (msg_dsz - msg_rem)); __skb_queue_tail(list, skb); } - hdr = buf_msg(skb_peek_tail(list)); + skb = skb_peek_tail(list); + if (!skb) + return; + hdr = buf_msg(skb); msg_set_last_bulk(hdr); msg_set_named_seqno(hdr, seqno); } @@ -219,7 +222,8 @@ void tipc_named_node_up(struct net *net, u32 dnode, u16 capabilities) read_lock_bh(&nt->cluster_scope_lock); named_distribute(net, &head, dnode, &nt->cluster_scope, seqno); - tipc_node_xmit(net, &head, dnode, 0); + if (!skb_queue_empty(&head)) + tipc_node_xmit(net, &head, dnode, 0); read_unlock_bh(&nt->cluster_scope_lock); } -- 2.43.0