Linux Kernel CVE-2026-98897: ksmbd Oplock Lease Break Deadlock Prevention
CVE-2026-98897 Published on October 23, 2026
ksmbd: don't hold ci->m_lock while waiting for a lease break ack
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: don't hold ci->m_lock while waiting for a lease break ack
When a cifs.ko client caches a read-handle (RH) lease via deferred close
and a conflicting open arrives, ksmbd breaks the lease and waits for the
acknowledgment in wait_for_break_ack() for up to OPLOCK_WAIT_TIME (35s).
__smb_break_all_levII_oplock() runs that wait while holding ci->m_lock
for read.
cifs.ko reacts to a handle-lease break by closing the deferred handle
rather than sending a lease break acknowledgment. That close path
(close_id_del_oplock() -> opinfo_del()) takes ci->m_lock for write and
is exactly what would wake the waiter, but it blocks on the read lock
held by the waiting thread. The break is then resolved only by the 35s
timeout, so xfstests generic/001 takes ~78s with leases enabled versus
~4s with oplocks only.
Collect the target opinfos (each pinned with a reference) while holding
ci->m_lock, then break them after releasing it, matching how
smb_grant_oplock() already breaks a conflicting lease using only a
reference. The reference keeps the opinfo (and its conn and lease)
alive across the unlocked window, and a close racing the break is
handled by the existing OPLOCK_CLOSING state check. Apply the same fix
to the parent lease break paths.
Products Associated with CVE-2026-98897
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Affected Versions
Linux:- Version d1c189c6cb8b0fb7b5ee549237d27889c40c2f8b and below 868c9038ffd4af39766d087f68c8f543a3f66635 is affected.
- Version d1c189c6cb8b0fb7b5ee549237d27889c40c2f8b and below 27a9bc968d4ae809a3f5ca2f2b136856ee613cb4 is affected.
- Version 16ece7c5645a68efca22a0a69a7718c8e50c3232 is affected.
- Version 6.6.35 and below 6.7 is affected.
- Version 6.9 is affected.
- Before 6.9 is unaffected.
- Version 6.18.53, <= 6.18.* is unaffected.
- Version 7.2, <= * is unaffected.