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CVE-2024-26923A-336268889ASB-A-336268889

af_unix: Fix garbage collector racing against connect()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 4.19.314, 5.4.275, 5.10.216, 5.15.156, 6.1.87, and 3 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: af_unix: Fix garbage collector racing against connect() Garbage collector does not take into account the risk of embryo getting enqueued during the garbage collection. If such embryo has a peer that carries SCM_RIGHTS, two consecutive passes of scan_children() may see a different set of children. Leading to an incorrectly elevated inflight count, and then a dangling pointer within the gc_inflight_list. sockets are AF_UNIX/SOCK_STREAM S is an unconnected socket L is a listening in-flight socket bound to addr, not in fdtable V's fd will be passed via sendmsg(), gets inflight count bumped connect(S, addr) sendmsg(S, [V]); close(V) __unix_gc() ---------------- ------------------------- ----------- NS = unix_create1() skb1 = sock_wmalloc(NS) L = unix_find_other(addr) unix_state_lock(L) unix_peer(S) = NS // V count=1 inflight=0 NS = unix_peer(S) skb2 = sock_alloc() skb_queue_tail(NS, skb2[V]) // V became in-flight // V count=2 inflight=1 close(V) // V count=1 inflight=1 // GC candidate condition met for u in gc_inflight_list: if (total_refs == inflight_refs) add u to gc_candidates // gc_candidates={L, V} for u in gc_candidates: scan_children(u, dec_inflight) // embryo (skb1) was not // reachable from L yet, so V's // inflight remains unchanged __skb_queue_tail(L, skb1) unix_state_unlock(L) for u in gc_candidates: if (u.inflight) scan_children(u, inc_inflight_move_tail) // V count=1 inflight=2 (!) If there is a GC-candidate listening socket, lock/unlock its state. This makes GC wait until the end of any ongoing connect() to that socket. After flipping the lock, a possibly SCM-laden embryo is already enqueued. And if there is another embryo coming, it can not possibly carry SCM_RIGHTS. At this point, unix_inflight() can not happen because unix_gc_lock is already taken. Inflight graph remains unaffected.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 · fixed in a36ae0ec2353015f0f6762e59f4c2dbc0c906423; From 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 · fixed in 343c5372d5e17b306db5f8f3c895539b06e3177f; From 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 · fixed in 2e2a03787f4f0abc0072350654ab0ef3324d9db3; From 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 · fixed in e76c2678228f6aec74b305ae30c9374cc2f28a51; From 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 · fixed in b75722be422c276b699200de90527d01c602ea7c; From 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 · fixed in 507cc232ffe53a352847893f8177d276c3b532a9; From 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 · fixed in dbdf7bec5c920200077d693193f989cb1513f009; From 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 · fixed in 47d8ac011fe1c9251070e1bd64cb10b48193ec51

  • Linux Linux

    2.6.23

  • KernelLinux

    From 2.6.23 · fixed in 4.19.314; From 4.20.0 · fixed in 5.4.275; From 5.5.0 · fixed in 5.10.216; From 5.11.0 · fixed in 5.15.156; From 5.16.0 · fixed in 6.1.87; From 6.2.0 · fixed in 6.6.28; From 6.7.0 · fixed in 6.8.7

  • :linux_kernel:Android

    From :0 · fixed in :2024-07-05

References 8

git.kernel.org