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af_unix: Fix garbage collector racing against connect() (Linux Linux)

CVE-2024-26923
HIGH 7.8

At a glance

Source
NVD
EPSS
EPSS 0.21 % · percentile 11 ()
State
PUBLISHED
Published
Updated
Assigner
Linux
NVD status
Modified

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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.

Weaknesses (CWE)

  • CWE-362 — Concurrent Execution using Shared Resource with Improper Synchronization

References

Scores

VersionScoreVectorScored by
CVSS 3.1HIGH 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HLinux
CVSS 3.1HIGH 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HNVD · 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Secondary)
CVSS 3.1MEDIUM 4.7CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:HNVD · nvd@nist.gov (Primary)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
Linux · Linuxaffected 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < a36ae0ec2353015f0f6762e59f4c2dbc0c906423 ; affected 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < 343c5372d5e17b306db5f8f3c895539b06e3177f ; affected 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < 2e2a03787f4f0abc0072350654ab0ef3324d9db3 ; affected 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < e76c2678228f6aec74b305ae30c9374cc2f28a51 ; affected 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < b75722be422c276b699200de90527d01c602ea7c ; affected 1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < 507cc232ffe53a352847893f8177d276c3b532a9
Linux · Linuxaffected 2.6.23 ; unaffected 0 < 2.6.23 ; unaffected 4.19.314 ≤ 4.19.* ; unaffected 5.4.275 ≤ 5.4.* ; unaffected 5.10.216 ≤ 5.10.* ; unaffected 5.15.156 ≤ 5.15.*

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD