In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
dibs: fix use-after-free of dmb_node in loopback attach\/detach\/unregister<\/p>\n
dibs_lo_attach_dmb(), dibs_lo_detach_dmb() and dibs_lo_unregister_dmb()
\nlook up the dmb_node under dmb_ht_lock, drop the lock and only then
\noperate on the node’s refcount. Nothing keeps the node alive across
\nthat window: __dibs_lo_unregister_dmb() removes the node from the hash
\ntable under the write lock and immediately frees it.<\/p>\n
A concurrent final put can therefore free the node between the lookup
\nand the refcount operation:<\/p>\n
CPU0 (attach) CPU1 (owner unregisters)<\/p>\n
read_lock_bh(&dmb_ht_lock)
\nfind dmb_node (refcnt == 1)
\nread_unlock_bh(&dmb_ht_lock)
\n refcount_dec_and_test() 1 -> 0
\n write_lock_bh(&dmb_ht_lock)
\n hash_del(&dmb_node->list)
\n write_unlock_bh(&dmb_ht_lock)
\n kfree(dmb_node)
\nrefcount_inc_not_zero(&dmb_node->refcnt) <– use-after-free<\/p>\n
The same window exists for the refcount_dec_and_test() calls in the
\ndetach and unregister paths.<\/p>\n
Close the race structurally by making hash table membership and the
\nrefcount transitions atomic with respect to each other:<\/p>\n
– Perform the final refcount_dec_and_test() and hash_del() in a single
\n dmb_ht_lock write-side critical section, in both the unregister and
\n the detach path. Freeing the node still happens after the lock is
\n dropped, which is safe because a node whose refcount reached zero has
\n left the hash table and can no longer be found.<\/p>\n
– This establishes the invariant that any node found in the hash table
\n holds at least one reference, and that the final reference can only
\n be dropped under the write lock. dibs_lo_attach_dmb() can thus take
\n its reference with a plain refcount_inc() while still holding the
\n read lock; refcount_inc_not_zero() is no longer needed.<\/p>\n
__dibs_lo_unregister_dmb() no longer touches the hash table and is
\nrenamed to dibs_lo_free_dmb() accordingly.<\/p>\n
Note: commit cc21191b584c ("dibs: Move data path to dibs layer") moved
\nthe code to its current location; the race was introduced earlier by
\ncommit c3a910f2380f ("net\/smc: implement DMB-merged operations of
\nloopback-ism").<\/p>\n
Tested SMC-D via ISM and dibs loopback.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
dibs: fix use-after-free of dmb_node in loopback attach\/detach\/unregister<\/p>\n
dibs_lo_attach_dmb(), dibs_lo_detach_dmb() and dibs_lo_u<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-7510","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/7510","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=7510"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=7510"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=7510"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}