In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
RDMA\/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds<\/p>\n
rxe_get_mcg() publishes a newly allocated multicast group in
\nrxe->mcg_tree before programming the backing Ethernet multicast address
\nwith rxe_mcast_add(), which runs outside mcg_lock. A local userspace
\nRDMA client reaches this path with ATTACH_MCAST on a UD QP; if
\nrxe_mcast_add() then returns an error (for example -ENODEV when the
\nbacking netdev has been removed, or a propagated dev_mc_add() error),
\nthe unwind frees the published group without removing it from the tree.
\nA later lookup of the same MGID dereferences the freed struct rxe_mcg
\nfrom __rxe_lookup_mcg().<\/p>\n
Fix this by keeping the new mcg private until rxe_mcast_add() succeeds.
\nSplit the tree publication into __rxe_publish_mcg(), call rxe_mcast_add()
\nbefore taking the tree reference, and free the still-private mcg on
\nfailure. Because the group is never visible in mcg_tree until the
\nmulticast address is programmed, no concurrent caller can look it up or
\nattach a QP to a group that is about to be torn down, so the error path
\nneeds no conditional unwind. If another caller publishes the same MGID
\nwhile the address is being programmed, the post-add re-check under
\nmcg_lock finds the winner; this caller then drops its private object and
\nbalances its own rxe_mcast_add() with rxe_mcast_del() before returning
\nthe winner.<\/p>\n
Reproduced by forcing the rxe_mcast_add() error return under KASAN:
\nwithout the change the next attach to the same MGID reports a
\nslab-use-after-free in __rxe_lookup_mcg(); with it the forced failure
\nreturns cleanly. A no-injection attach\/detach regression, including a
\ntwo-QP shared join\/leave and re-attach, stays KASAN- and leak-clean.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
RDMA\/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds<\/p>\n
rxe_get_mcg() publishes a newly allocated multicast group i<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-33429","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/33429","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=33429"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=33429"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=33429"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}