CyberRota Analysis
AI-GeneratedThe vulnerability affects the Linux kernel's TIPC (Transparent Inter-Process Communication) subsystem, where a race condition can lead to a use-after-free scenario. This occurs when a link pointer is cached and subsequently dereferenced after it has been freed by another process, potentially allowing for arbitrary code execution or system crashes. Organizations using Linux systems with TIPC should prioritize patching this vulnerability to mitigate risks associated with memory corruption and system instability.
Original NVD Description
In the Linux kernel, the following vulnerability has been resolved: tipc: read le->link under the node lock in tipc_node_link_down() tipc_node_link_down() caches the link pointer before taking n->lock: struct tipc_link *l = le->link; /* unlocked */ if (!l) return; tipc_node_write_lock(n); if (!tipc_link_is_establishing(l)) { /* deref l */ ... tipc_link_reset(l); /* write into l */ if (delete) { kfree(l); le->link = NULL; The delete=true caller frees that very object under n->lock, so the lock does not protect the cached pointer against it: - CPU A, delete=false: tipc_rcv() on TIPC_LINK_DOWN_EVT, or the link supervision timer via tipc_node_timeout(), reads l unlocked and then dereferences it under n->lock; - CPU B, delete=true: netlink TIPC_NL_BEARER_DISABLE -> bearer_disable() -> tipc_node_delete_links() -> tipc_node_link_down(n, bearer_id, true) -> kfree(l). The link is freed with plain kfree(), not kfree_rcu(), and for UDP bearers disable_media() only schedules the asynchronous cleanup_bearer() work, so its synchronize_net() runs after the links are already gone. An in-flight CPU A that has read l therefore dereferences freed memory once B frees it: a use-after-free read in tipc_link_is_establishing(), and a use-after-free write via tipc_link_reset() on the establishing branch. The following trace was captured on 7.2.0-rc5-00284-gaf39eb111ce6: BUG: KASAN: slab-use-after-free in tipc_link_is_establishing (net/tipc/link.c:285) Read of size 4 at addr ffff88802e2aa068 by task swapper/2/0 tipc_link_is_establishing (net/tipc/link.c:285) tipc_node_link_down (net/tipc/node.c:1076) tipc_node_timeout (net/tipc/node.c:843) Allocated by task 9549: tipc_link_create (net/tipc/link.c:490) tipc_node_check_dest (net/tipc/node.c:1279) tipc_disc_rcv (net/tipc/discover.c:252) tipc_udp_recv (net/tipc/udp_media.c:389) Freed by task 9549: tipc_node_link_down (net/tipc/node.c:1084) tipc_node_delete_links (net/tipc/node.c:1320) bearer_disable (net/tipc/bearer.c:414) __tipc_nl_bearer_disable (net/tipc/bearer.c:992) Move the le->link read inside tipc_node_write_lock(), so it is serialised against the kfree() in the delete path. A racing teardown now either has not run yet, and we see a valid link, or has already run, and we see NULL.