RDMA/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98360
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-06 09:18:29 UTC
Updated2026-10-19 10:18:38 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: RDMA/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds rxe_get_mcg() publishes a newly allocated multicast group in rxe->mcg_tree before programming the backing Ethernet multicast address with rxe_mcast_add(), which runs outside mcg_lock. A local userspace RDMA client reaches this path with ATTACH_MCAST on a UD QP; if rxe_mcast_add() then returns an error (for example -ENODEV when the backing netdev has been removed, or a propagated dev_mc_add() error), the unwind frees the published group without removing it from the tree. A later lookup of the same MGID dereferences the freed struct rxe_mcg from __rxe_lookup_mcg(). Fix this by keeping the new mcg private until rxe_mcast_add() succeeds. Split the tree publication into __rxe_publish_mcg(), call rxe_mcast_add() before taking the tree reference, and free the still-private mcg on failure. Because the group is never visible in mcg_tree until the multicast address is programmed, no concurrent caller can look it up or attach a QP to a group that is about to be torn down, so the error path needs no conditional unwind. If another caller publishes the same MGID while the address is being programmed, the post-add re-check under mcg_lock finds the winner; this caller then drops its private object and balances its own rxe_mcast_add() with rxe_mcast_del() before returning the winner. Reproduced by forcing the rxe_mcast_add() error return under KASAN: without the change the next attach to the same MGID reports a slab-use-after-free in __rxe_lookup_mcg(); with it the forced failure returns cleanly. A no-injection attach/detach regression, including a two-QP shared join/leave and re-attach, stays KASAN- and leak-clean.

Risk And Classification

Primary CVSS: v3.1 7 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001760000 probability, percentile 0.065250000 (date 2026-10-06)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7HIGHCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7HIGHCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected a926a903b7dc39a8a949150258c09290998dd812 ddb43ac0926d4a931bc9b7744b93627f627457e5 git Not specified
CNA Linux Linux affected a926a903b7dc39a8a949150258c09290998dd812 c79a789aa15180a1543b5db49c343d12e3ec214d git Not specified
CNA Linux Linux affected a926a903b7dc39a8a949150258c09290998dd812 faae1fb4ccf8205806a8802c008798dabeb0205b git Not specified
CNA Linux Linux affected a926a903b7dc39a8a949150258c09290998dd812 02c0a2fa69c16248a7432af8a6d64ab2a73a5283 git Not specified
CNA Linux Linux affected a926a903b7dc39a8a949150258c09290998dd812 d4fc4e37f8a143b0fe83b42c8fb48cf542154fee git Not specified
CNA Linux Linux affected a926a903b7dc39a8a949150258c09290998dd812 1caceeb2d74bbe88223aea55eb8626b4c5f076fd git Not specified
CNA Linux Linux affected 5.18 Not specified
CNA Linux Linux unaffected 5.18 semver Not specified
CNA Linux Linux unaffected 6.1.189 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.158 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.112 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.54 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.8 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/d4fc4e37f8a143b0fe83b42c8fb48cf542154fee 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ddb43ac0926d4a931bc9b7744b93627f627457e5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1caceeb2d74bbe88223aea55eb8626b4c5f076fd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/faae1fb4ccf8205806a8802c008798dabeb0205b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/02c0a2fa69c16248a7432af8a6d64ab2a73a5283 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c79a789aa15180a1543b5db49c343d12e3ec214d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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