tcp: fix AO info use-after-free in tcp_ao_connect_init()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80850
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-04 16:18:13 UTC
Updated2026-09-04 16:18:13 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: tcp: fix AO info use-after-free in tcp_ao_connect_init() tcp_v4_connect() adds a SYN-SENT socket to the ehash before calling tcp_connect(). If TCP-AO is configured, tcp_connect() first verifies that a key matches the peer and the bound device's current L3 master. tcp_ao_connect_init() later resolves the L3 master again and removes keys which do not match it. The socket lock does not stabilize the bound device's VRF membership. Detaching the device from its VRF between the initial validation and the L3-master calculation in tcp_ao_connect_init() can therefore make the validation succeed while initialization observes the default L3 domain and removes the only key. The subsequent AO lookup then fails, so the no-key path clears tp->ao_info and frees it directly. The receive path can find the socket in the ehash and load tp->ao_info under RCU before acquiring the socket lock. A reader which loaded the old pointer can thus continue into tcp_inbound_ao_hash() after the direct free. The issue was found during a static audit of TCP-AO object lifetime. An unprivileged reproducer in self-created user and network namespaces raced connect() with detaching a veth from its VRF while sending TCP-AO segments. It triggered the same KASAN report on two fresh boots: BUG: KASAN: slab-use-after-free in tcp_inbound_ao_hash+0x585/0x19f0 Write of size 8 at addr ffff88800bf88128 by task tcp_ao_vrf_race/232 Call Trace: tcp_inbound_ao_hash+0x585/0x19f0 tcp_inbound_hash+0x677/0xa80 tcp_v4_rcv+0x1c3e/0x3ab0 Allocated by task 235: tcp_ao_alloc_info+0x43/0xf0 tcp_ao_add_cmd+0xdf7/0x13b0 do_tcp_setsockopt+0x168c/0x2640 Freed by task 235: kfree+0x1b8/0x550 tcp_connect+0x252/0x4f00 tcp_v4_connect+0x1114/0x1720 The bad address is 40 bytes inside the freed 128-byte object, matching the tcp_ao_info counters.key_not_found field. The two runs used 1000 attempts each, reached the no-key path 366 and 411 times, and produced one and two KASAN reports respectively. With this change, the same reproducer reached the no-key path 366 times in 1000 attempts without a KASAN report or oops. Use tcp_ao_destroy_sock() for the no-key path. It unpublishes the AO info, updates the socket memory and static-key accounting, and defers the free until after an RCU grace period. Also drop the WARN_ON_ONCE() and its stale comment. The VRF detach race makes the no-key state reachable during normal operation, so it is a handled condition rather than an impossible assertion. On panic_on_warn kernels the WARN would turn this handled race into a kernel panic.

Risk And Classification

EPSS: 0.001710000 probability, percentile 0.067040000 (date 2026-09-07)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 248411b8cb8974a1e1c8e43123c1e682fbd64969 594ba77210a1f065832211851a2d7e14d11fcbdb git Not specified
CNA Linux Linux affected 248411b8cb8974a1e1c8e43123c1e682fbd64969 70051a57786d5b23f059fbaf5c8241eca14d42ed git Not specified
CNA Linux Linux affected 248411b8cb8974a1e1c8e43123c1e682fbd64969 284d7fd0eec8774bd6214921fbf525cf907c590e git Not specified
CNA Linux Linux affected 248411b8cb8974a1e1c8e43123c1e682fbd64969 d17e88b6b60ff4ef64e0dd1444f935cb13dee1cd git Not specified
CNA Linux Linux affected 248411b8cb8974a1e1c8e43123c1e682fbd64969 ea30dc5267e367b8a5e1e06cc074f813bcbf18b2 git Not specified
CNA Linux Linux affected 6.7 Not specified
CNA Linux Linux unaffected 6.7 semver Not specified
CNA Linux Linux unaffected 6.12.108 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.49 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.13 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2.3 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/594ba77210a1f065832211851a2d7e14d11fcbdb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d17e88b6b60ff4ef64e0dd1444f935cb13dee1cd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/284d7fd0eec8774bd6214921fbf525cf907c590e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/70051a57786d5b23f059fbaf5c8241eca14d42ed 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ea30dc5267e367b8a5e1e06cc074f813bcbf18b2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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