CVE-2024-26923

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < a36ae0ec2353015f0f6762e59f4c2dbc0c906423affected
LinuxLinux1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < 343c5372d5e17b306db5f8f3c895539b06e3177faffected
LinuxLinux1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < 2e2a03787f4f0abc0072350654ab0ef3324d9db3affected
LinuxLinux1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < e76c2678228f6aec74b305ae30c9374cc2f28a51affected
LinuxLinux1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < b75722be422c276b699200de90527d01c602ea7caffected
LinuxLinux1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < 507cc232ffe53a352847893f8177d276c3b532a9affected
LinuxLinux1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < dbdf7bec5c920200077d693193f989cb1513f009affected
LinuxLinux1fd05ba5a2f2aa8e7b9b52ef55df850e2e7d54c9 < 47d8ac011fe1c9251070e1bd64cb10b48193ec51affected
LinuxLinux2.6.23affected
LinuxLinux0 < 2.6.23unaffected
LinuxLinux4.19.314 <= 4.19.*unaffected
LinuxLinux5.4.275 <= 5.4.*unaffected
LinuxLinux5.10.216 <= 5.10.*unaffected
LinuxLinux5.15.156 <= 5.15.*unaffected
LinuxLinux6.1.87 <= 6.1.*unaffected
LinuxLinux6.6.28 <= 6.6.*unaffected
LinuxLinux6.8.7 <= 6.8.*unaffected
LinuxLinux6.9 <= *unaffected

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: total

CVE Program Container

Additional References

Additional References

References