In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
tipc: read le->link under the node lock in tipc_node_link_down()<\/p>\n
tipc_node_link_down() caches the link pointer before taking n->lock:<\/p>\n
\tstruct tipc_link *l = le->link;\t\t\/* unlocked *\/<\/p>\n
\tif (!l)
\n\t\treturn;
\n\ttipc_node_write_lock(n);
\n\tif (!tipc_link_is_establishing(l)) {\t\/* deref l *\/
\n\t…
\n\t\ttipc_link_reset(l);\t\t\/* write into l *\/
\n\tif (delete) {
\n\t\tkfree(l);
\n\t\tle->link = NULL;<\/p>\n
The delete=true caller frees that very object under n->lock, so the lock
\ndoes not protect the cached pointer against it:<\/p>\n
– CPU A, delete=false: tipc_rcv() on TIPC_LINK_DOWN_EVT, or the link
\n supervision timer via tipc_node_timeout(), reads l unlocked and then
\n dereferences it under n->lock;
\n – CPU B, delete=true: netlink TIPC_NL_BEARER_DISABLE -> bearer_disable()
\n -> tipc_node_delete_links() -> tipc_node_link_down(n, bearer_id, true)
\n -> kfree(l).<\/p>\n
The link is freed with plain kfree(), not kfree_rcu(), and for UDP bearers
\ndisable_media() only schedules the asynchronous cleanup_bearer() work, so
\nits synchronize_net() runs after the links are already gone. An in-flight
\nCPU A that has read l therefore dereferences freed memory once B frees it:
\na use-after-free read in tipc_link_is_establishing(), and a use-after-free
\nwrite via tipc_link_reset() on the establishing branch.<\/p>\n
The following trace was captured on 7.2.0-rc5-00284-gaf39eb111ce6:<\/p>\n
BUG: KASAN: slab-use-after-free in tipc_link_is_establishing (net\/tipc\/link.c:285)
\n Read of size 4 at addr ffff88802e2aa068 by task swapper\/2\/0
\n tipc_link_is_establishing (net\/tipc\/link.c:285)
\n tipc_node_link_down (net\/tipc\/node.c:1076)
\n tipc_node_timeout (net\/tipc\/node.c:843)
\n Allocated by task 9549:
\n tipc_link_create (net\/tipc\/link.c:490)
\n tipc_node_check_dest (net\/tipc\/node.c:1279)
\n tipc_disc_rcv (net\/tipc\/discover.c:252)
\n tipc_udp_recv (net\/tipc\/udp_media.c:389)
\n Freed by task 9549:
\n tipc_node_link_down (net\/tipc\/node.c:1084)
\n tipc_node_delete_links (net\/tipc\/node.c:1320)
\n bearer_disable (net\/tipc\/bearer.c:414)
\n __tipc_nl_bearer_disable (net\/tipc\/bearer.c:992)<\/p>\n
Move the le->link read inside tipc_node_write_lock(), so it is serialised
\nagainst the kfree() in the delete path. A racing teardown now either has
\nnot run yet, and we see a valid link, or has already run, and we see NULL.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
tipc: read le->link under the node lock in tipc_node_link_down()<\/p>\n
tipc_node_link_down() caches the link pointer before taking n->lo<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-11215","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/11215","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=11215"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=11215"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=11215"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}