ksmbd: fix tree connection use-after-free in smb2_tree_connect()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-89788
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-16 09:17:09 UTC
Updated2026-09-16 09:17:09 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ksmbd: fix tree connection use-after-free in smb2_tree_connect() ksmbd_tree_conn_connect() publishes a new tree connection in sess->tree_conns with a single reference and returns its pointer to smb2_tree_connect(). The handler continues to initialize the object and build the response after publication. A concurrent session logoff can erase the connection and drop that reference, freeing the object while the handler still uses it. BUG: KASAN: slab-use-after-free in smb2_tree_connect+0xe3d/0xf90 smb2_tree_connect (fs/smb/server/smb2pdu.c:2872) handle_ksmbd_work process_one_work worker_thread kthread After xa_store() succeeds, take a second reference before releasing tree_conns_lock. The original reference belongs to the xarray entry and the second belongs to the creating smb2_tree_connect() handler. Keep the references balanced in every path: - On normal exit or an error after publication, smb2_tree_connect() drops its creator reference. Error cleanup also calls ksmbd_tree_conn_disconnect(), which drops the xarray reference only if it removes the exact entry. - SMB2 TREE_DISCONNECT uses the same helper to remove the entry and drop its xarray reference. The request's existing lookup reference remains owned by the request and is released by the existing cleanup. - Session LOGOFF removes each entry and drops its xarray reference. If it wins the race, later cleanup sees that the entry is gone and does not drop that reference again. To enforce this ownership, claim the disconnected state and erase the exact entry atomically under tree_conns_lock. This guarantees one drop for the xarray reference and one drop by each in-flight user, regardless of which teardown path wins. If logoff removes the entry before initialization completes, fail the connect instead of marking the detached object TREE_CONNECTED.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 33b235a6e6ebe0f05f3586a71e8d281d00f71e2e 4e30fbd26e84efa2e5cbec4eb11e126ac0c79313 git Not specified
CNA Linux Linux affected 33b235a6e6ebe0f05f3586a71e8d281d00f71e2e b5ec6c462aab1062cf5d1e667ba7c6442f737055 git Not specified
CNA Linux Linux affected dd45db4d9bbc8f122a9b4db5ce94ae29fcf03d3c git Not specified
CNA Linux Linux affected 7b58ee8d0b91359554cf219cd4f33872ea2afd66 git Not specified
CNA Linux Linux affected 5.15.145 5.16 semver Not specified
CNA Linux Linux affected 6.1.71 6.2 semver Not specified
CNA Linux Linux affected 6.6 Not specified
CNA Linux Linux unaffected 6.6 semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/4e30fbd26e84efa2e5cbec4eb11e126ac0c79313 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b5ec6c462aab1062cf5d1e667ba7c6442f737055 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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