CVE-2026-99053: tipc: hold a reference to nodes found by link name
In the Linux kernel, the following vulnerability has been resolved:
tipc: hold a reference to nodes found by link name
tipcnodefindbyname() returns a node after dropping its RCU read lock without taking a reference. The LINKSET, LINKGET and LINKRESETSTATS handlers then lock and access the node, racing with timer-driven cleanup of a down peer. Generic netlink serialization does not exclude the node timer.
The following interleaving can leave a handler using a freed node:
CPU 0: find the node under RCU and release the node read lock CPU 1: tipcnodetimeout() clears the links and unlinks the down node CPU 1: drop the list and timer references, queuing tipcnodefree() CPU 0: leave the RCU read-side critical section CPU 1: complete the grace period and free the node CPU 0: acquire the node lock through the stale pointer
LINKSET also uses the node's media address after releasing the node lock, when passing queued packets to tipcbearerxmit().
KASAN on v7.3-rc5 reported:
BUG: KASAN: slab-use-after-free in rawreadlockbh Write of size 4 at addr ffff88807e06f008 by task poc/92 Call Trace: rawreadlockbh kernel/locking/spinlock.c:287 tipcnlnodesetlink net/tipc/node.c:2475 genlfamilyrcvmsgdoit net/netlink/genetlink.c:1114 genlrcvmsg net/netlink/genetlink.c:1209 netlinkrcvskb net/netlink/afnetlink.c:2575
Allocated by task 0: tipcnodecreate net/tipc/node.c:539 tipcnodecheckdest net/tipc/node.c:1196 tipcdiscrcv net/tipc/discover.c:252
Freed by task 92: kfree mm/slub.c:6801 rcucore kernel/rcu/tree.c:2919
Last potentially related work creation: callrcucommon.constprop.0 kernel/rcu/tree.c:3181 tipcnodetimeout net/tipc/node.c:814
Acquire a reference to the selected node with krefgetunlesszero() before leaving RCU, returning NULL if the node has already been released. Release that reference on every caller exit after the last node access, including transmission in LINKSET. Keep the existing link lookup order and locking so concurrent link removal still takes the existing error paths.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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In tipc_node_find_by_name() callers, acquire a reference to the selected node with kref_get_unless_zero() before leaving RCU, return NULL if the node has already been released, and release that reference on every caller exit after the last node access, including LINK_SET transmission; preserve the existing link lookup order and locking.
Event History
Frequently Asked Questions
What conditions are needed to trigger the race?
A TIPC generic netlink LINK_SET, LINK_GET, or LINK_RESET_STATS request must operate on a node found by link name while timer-driven cleanup is removing a down peer. The handler can then retain and lock a stale node pointer after the node has been freed.
Which operation has additional exposure beyond locking the stale node?
LINK_SET also accesses the node's media address after releasing the node lock when passing queued packets to tipc_bearer_xmit(). This creates an additional use-after-free access path.
How might this issue appear during testing?
KASAN reported a slab-use-after-free in _raw_read_lock_bh, reached from tipc_nl_node_set_link. The reported observation was on v7.3-rc5.