CriticalFix available

nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke nfsd4_alloc_layout_stateid reads fp->fi_deleg_file without holding fi_lock when the parent stateid is a delegation. A concurrent delegation revoke via the laundromat can clear fi_deleg_file under fi_lock, causing nfsd_file_get() to return NULL and triggering the BUG_ON. This race is client-reachable: two NFS clients can trigger it by having one hold a delegation while another opens the same file to force a recall. When the first client doesn't respond to the recall, the laundromat revokes it. A concurrent LAYOUTGET from any client using the delegation stateid hits the race window. Fix this by taking fi_lock around the fi_deleg_file read in the SC_TYPE_DELEG path, matching the locking discipline of the find_any_file() arm, and replacing the BUG_ON with a graceful error return that cleans up the partially-initialized layout stateid.

Products: Kernel
Affected versions: Not specified
Fixed versions: 6.1.191, 6.12.109, 6.18.50, 6.6.160, 7.2.4
CVEs: CVE-2026-89686
Confirmed fixed CVEs: Not specified
Updated in this feed: 8 Nov 2026, 01:28 UTC · Revision 1

Source evidence

nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke

core-osv · Original source

Published 11 Sept 2026, 19:46 UTC

osv:CVE-2026-89686

Kernel

Fixed versions: 6.1.191, 6.6.160, 6.12.109, 6.18.50, 7.2.4

Complete source record

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    "title": "nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke nfsd4_alloc_layout_stateid reads fp->fi_deleg_file without holding fi_lock when the parent stateid is a delegation. A concurrent delegation revoke via the laundromat can clear fi_deleg_file under fi_lock, causing nfsd_file_get() to return NULL and triggering the BUG_ON. This race is client-reachable: two NFS clients can trigger it by having one hold a delegation while another opens the same file to force a recall. When the first client doesn't respond to the recall, the laundromat revokes it. A concurrent LAYOUTGET from any client using the delegation stateid hits the race window. Fix this by taking fi_lock around the fi_deleg_file read in the SC_TYPE_DELEG path, matching the locking discipline of the find_any_file() arm, and replacing the BUG_ON with a graceful error return that cleans up the partially-initialized layout stateid.",
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