Re: [PATCH net v2] tipc: fix NULL deref in tipc_named_node_up() on empty publication list
From: Simon Horman <horms@kernel.org>
Date: 2026-07-13 13:36:26
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This is an AI-generated review of your patch. The human sending this email has considered the AI review valid, or at least plausible. Full review at: https://sashiko.dev --- tipc: fix NULL deref in tipc_named_node_up() on empty publication list This commit fixes a NULL pointer dereference in tipc_named_node_up() that occurs when the cluster_scope publication list is empty. The fix introduces an early return to avoid calling named_distribute() with an empty list.
quoted hunk ↗ jump to hunk
diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c index ba4f4906e13b7..60ccaa862162c 100644 --- a/net/tipc/name_distr.c +++ b/net/tipc/name_distr.c@@ -218,6 +218,10 @@ void tipc_named_node_up(struct net *net, u32 dnode, u16 capabilities) spin_unlock_bh(&tn->nametbl_lock); read_lock_bh(&nt->cluster_scope_lock); + if (list_empty(&nt->cluster_scope)) { + read_unlock_bh(&nt->cluster_scope_lock); + return; + }
[Severity: Critical]
Does this early return prevent the transmission of the last_bulk
synchronization message to the peer node?
In tipc_named_dequeue(), the peer node sets *open = true only when receiving
a message where msg_is_last_bulk(hdr) is true:
net/tipc/name_distr.c:tipc_named_dequeue() {
...
if (*open && (*rcv_nxt == seqno)) {
(*rcv_nxt)++;
__skb_unlink(skb, namedq);
...
return skb;
}
...
}
If *open is false, all subsequent non-bulk name publications will fail this
sequence check and remain in the namedq indefinitely.
Without sending the last_bulk message, could this cause a permanent stall
of name table updates and an unbounded memory leak of socket buffers on the
peer node?
named_distribute(net, &head, dnode, &nt->cluster_scope, seqno);
[Severity: High]
This isn't a bug introduced by this patch, but looking at named_distribute()
called here, what happens if buffer allocation fails during the loop?
Inside named_distribute():
net/tipc/name_distr.c:named_distribute() {
...
if (!skb) {
skb = named_prepare_buf(net, PUBLICATION, msg_rem, dnode);
if (!skb) {
pr_warn("Bulk publication failure\n");
return;
}
...
}
If the function returns early due to allocation failure, the messages
already added to the queue are transmitted by tipc_node_xmit(), but none
of them will have the last_bulk flag set since that happens at the very end
of the function.
Could this also prevent the receiving node from transitioning its named_open
state to true, leading to the exact same permanent stall and memory leak of
subsequent normal name publications?
tipc_node_xmit(net, &head, dnode, 0); read_unlock_bh(&nt->cluster_scope_lock);