nfsd: clear CALLBACK_RUNNING on failed delegation recall queue

Overview

In the Linux kernel, the following vulnerability has been resolved:

nfsd: clear CALLBACK_RUNNING on failed delegation recall queue

nfsd_break_one_deleg() sets NFSD4_CALLBACK_RUNNING via test_and_set_bit at entry to serialize recall work, then calls nfsd4_run_cb() to queue the recall. When the queue attempt fails the refcount bump is undone, but the RUNNING bit is left set. The only site that clears the bit is nfsd41_destroy_cb() (fs/nfsd/nfs4callback.c), which runs from the workqueue and is therefore unreachable when nothing was queued.

The bit becomes a permanent latch on dp->dl_recall.cb_flags: every subsequent break_lease() on the same delegation hits the early-return guard in nfsd_break_one_deleg() and silently skips the recall, so the delegation is never broken and the conflicting open or lock stalls.

Fix by clearing NFSD4_CALLBACK_RUNNING on the !queued branch alongside the refcount_dec.

Affected

• Linux >= 1054e8ffc5c492f341bdf1888b882f1d163dd3d8 < b137930ee52e3ef38915a3511d4c070463b63a32
• Linux >= 1054e8ffc5c492f341bdf1888b882f1d163dd3d8 < cb2d0c4d1b3d301d042ed61365eaa8cb0141a254
• Linux >= 1054e8ffc5c492f341bdf1888b882f1d163dd3d8 < b036727d334b1b7cd4c1f1fba3b59ba93a6bbe96
• Linux 6.15

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat OpenShift Container Platform 4 · updated 2026-09-15 · vex