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CVE PROGRAM SOURCE RECORD7.8 High

CVE-2024-26923

af_unix: Fix garbage collector racing against connect()

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Status
Published
Published
Updated
Assigning organization
Linux

Description

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 to < a36ae0ec2353015f0f6762e59f4c2dbc0c906423affected
  • 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 to < 343c5372d5e17b306db5f8f3c895539b06e3177faffected
  • 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 to < 2e2a03787f4f0abc0072350654ab0ef3324d9db3affected
  • 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 to < e76c2678228f6aec74b305ae30c9374cc2f28a51affected
  • 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 to < b75722be422c276b699200de90527d01c602ea7caffected
  • 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 to < 507cc232ffe53a352847893f8177d276c3b532a9affected
  • 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 to < dbdf7bec5c920200077d693193f989cb1513f009affected
  • 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 to < 47d8ac011fe1c9251070e1bd64cb10b48193ec51affected

Linux Linux

Default version status: affected

  • 2.6.23affected
  • 0 to < 2.6.23unaffected
  • 4.19.314 to ≤ 4.19.*unaffected
  • 5.4.275 to ≤ 5.4.*unaffected
  • 5.10.216 to ≤ 5.10.*unaffected
  • 5.15.156 to ≤ 5.15.*unaffected
  • 6.1.87 to ≤ 6.1.*unaffected
  • 6.6.28 to ≤ 6.6.*unaffected
  • 6.8.7 to ≤ 6.8.*unaffected
  • 6.9 to ≤ *unaffected

References