ipc/shm: serialize orphan cleanup with shm_nattch updates

Summary

In the Linux kernel, the following vulnerability has been resolved: ipc/shm: serialize orphan cleanup with shm_nattch updates shm_destroy_orphaned() walks the shm idr under shm_ids(ns).rwsem, but that does not serialize all fields tested by shm_may_destroy(). In particular, shm_nattch is updated while holding shm_perm.lock, and attach paths can do that without holding the rwsem. Do not decide that an orphaned segment is unused before taking the object lock. Move the shm_may_destroy() check under shm_perm.lock, matching the other destroy paths, and unlock the segment when it no longer qualifies for removal.

Timeline

1. Jun 24, 2026, 7:14 AM UTCCVE published
2. Oct 15, 2026, 1:21 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 4c677e2eefdba9c5bfc4474e2e91b26ae8458a1d · fixed in b1e9aef48e4d8a0c1b54fb913077b0824ed7d650; From 4c677e2eefdba9c5bfc4474e2e91b26ae8458a1d · fixed in 92cda2593cf2ed25b0e9d78e5e6d8303bba1a064; From 4c677e2eefdba9c5bfc4474e2e91b26ae8458a1d · fixed in 1f0d01e35dbb228084d5187212e32c91a30dcbeb; From 4c677e2eefdba9c5bfc4474e2e91b26ae8458a1d · fixed in 6560be3f6a5bb84f006f184f0c966747bb58e1a3; From 4c677e2eefdba9c5bfc4474e2e91b26ae8458a1d · fixed in b5107b4ce3ad45fcf369ee2058c8910620f4b5a8; From 4c677e2eefdba9c5bfc4474e2e91b26ae8458a1d · fixed in db752ebfdaf2c7f27cd9690ef48b616af068319c; From 4c677e2eefdba9c5bfc4474e2e91b26ae8458a1d · fixed in 030bbc857bd51d4b25a90d931d3f8775ef22823a; From 4c677e2eefdba9c5bfc4474e2e91b26ae8458a1d · fixed in 2e5c6f4fd4001562781e99bbfc7f1f0127187542

• Linux Linux

  3.1

• KernelLinux

  From 3.1.0 · fixed in 5.10.259; From 5.11.0 · fixed in 5.15.210; From 5.16.0 · fixed in 6.1.176; From 6.2.0 · fixed in 6.6.143; From 6.7.0 · fixed in 6.12.94; From 6.13.0 · fixed in 6.18.36; From 6.19.0 · fixed in 7.0.13

References 8