tipc: read le->link under the node lock in tipc_node_link_down()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74609
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-22 16:16:33 UTC
Updated2026-08-22 16:16:33 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 73f646cec35477b5099d7e952297cb9e1855be45 2be741ad565c610871a6a95062c12c39da7168fd git Not specified
CNA Linux Linux affected 73f646cec35477b5099d7e952297cb9e1855be45 69d209461c110388710e483a130caf051e4fd09a git Not specified
CNA Linux Linux affected 73f646cec35477b5099d7e952297cb9e1855be45 de017c22135f545ca4e65d1eada22887b64958eb git Not specified
CNA Linux Linux affected 73f646cec35477b5099d7e952297cb9e1855be45 47ba70891b10b2feb52462086b7fcd2ad75d3ce3 git Not specified
CNA Linux Linux affected 73f646cec35477b5099d7e952297cb9e1855be45 a714d62513befef37f71f4ae89bb1fe173b65f2e git Not specified
CNA Linux Linux affected 73f646cec35477b5099d7e952297cb9e1855be45 c3f2347a47754eac690967cfd82cb6d559817b07 git Not specified
CNA Linux Linux affected 73f646cec35477b5099d7e952297cb9e1855be45 5558a8312452ddb21eff22b1cbd84302ad951944 git Not specified
CNA Linux Linux affected 73f646cec35477b5099d7e952297cb9e1855be45 cba9ccb47e9fa4cc77692fb896cc5ab57a667882 git Not specified
CNA Linux Linux affected 4.4 Not specified
CNA Linux Linux unaffected 4.4 semver Not specified
CNA Linux Linux unaffected 5.10.265 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.216 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.183 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.152 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.104 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.45 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.9 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/5558a8312452ddb21eff22b1cbd84302ad951944 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c3f2347a47754eac690967cfd82cb6d559817b07 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/47ba70891b10b2feb52462086b7fcd2ad75d3ce3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cba9ccb47e9fa4cc77692fb896cc5ab57a667882 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/de017c22135f545ca4e65d1eada22887b64958eb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/69d209461c110388710e483a130caf051e4fd09a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2be741ad565c610871a6a95062c12c39da7168fd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a714d62513befef37f71f4ae89bb1fe173b65f2e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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