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

ksmbd: only rebind the reopened file's own oplock on durable reconnect

ksmbd_reopen_durable_fd() walks the inode's m_op_list and rebinds every
detached oplock to the reconnecting session:

list_for_each_entry_rcu(op, &ci->m_op_list, op_entry,
lockdep_is_held(&ci->m_lock)) {
if (op->conn)
continue;
op->conn = ksmbd_conn_get(fp->conn);
op->sess = work->sess;
}

The only key is op->conn == NULL, which every detached durable handle on
that inode matches, not just the one owned by fp. When two sessions hold
durable handles on the same file and both disconnect, reconnecting one of
them adopts the other session's oplock: op->sess is overwritten with the
reconnecting session without taking a reference on it, while op->conn
pins the connection.

The sibling teardown path, session_fd_check(), keys on the identity of
the connection being torn down (op->conn == conn) rather than on shared
state, and so does not have this problem.

Once the adopting session is destroyed, ksmbd_session_destroy() frees it
while the foreign oplock still points at it. The reader in
ksmbd_close_fd_app_instance_id() validates only opinfo->conn, which is
still live thanks to the reference taken above, and then dereferences the
stale session:

if (!opinfo->conn) {
up_read(&fp->f_ci->m_lock);
goto out;
}

ft = &opinfo->sess->file_table;
write_lock(&ft->lock);

BUG: KASAN: slab-use-after-free in _raw_write_lock+0x74/0xd0
Write of size 4 at addr ffff88810a970528 by task kworker/0:0/9
Workqueue: ksmbd-io handle_ksmbd_work
Call Trace:
_raw_write_lock+0x74/0xd0
ksmbd_close_fd_app_instance_id+0x183/0x410
smb2_open+0x1346/0x4430
handle_ksmbd_work+0x2bb/0x7b0

Reached from an authenticated session against a share with the default
durable-handle and oplock configuration: two sessions open the same file
with a durable-v2 handle and an RH lease under distinct AppInstanceIds,
both log off, one reconnects with DH2C, and a later durable-v2 create
carrying the other AppInstanceId walks into the freed session.

Constrain the loop to the oplock owned by the file being reopened.
Published: 2026-09-11
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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History

Sat, 12 Sep 2026 07:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-416

Fri, 11 Sep 2026 23:45:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: ksmbd: only rebind the reopened file's own oplock on durable reconnect ksmbd_reopen_durable_fd() walks the inode's m_op_list and rebinds every detached oplock to the reconnecting session: list_for_each_entry_rcu(op, &ci->m_op_list, op_entry, lockdep_is_held(&ci->m_lock)) { if (op->conn) continue; op->conn = ksmbd_conn_get(fp->conn); op->sess = work->sess; } The only key is op->conn == NULL, which every detached durable handle on that inode matches, not just the one owned by fp. When two sessions hold durable handles on the same file and both disconnect, reconnecting one of them adopts the other session's oplock: op->sess is overwritten with the reconnecting session without taking a reference on it, while op->conn pins the connection. The sibling teardown path, session_fd_check(), keys on the identity of the connection being torn down (op->conn == conn) rather than on shared state, and so does not have this problem. Once the adopting session is destroyed, ksmbd_session_destroy() frees it while the foreign oplock still points at it. The reader in ksmbd_close_fd_app_instance_id() validates only opinfo->conn, which is still live thanks to the reference taken above, and then dereferences the stale session: if (!opinfo->conn) { up_read(&fp->f_ci->m_lock); goto out; } ft = &opinfo->sess->file_table; write_lock(&ft->lock); BUG: KASAN: slab-use-after-free in _raw_write_lock+0x74/0xd0 Write of size 4 at addr ffff88810a970528 by task kworker/0:0/9 Workqueue: ksmbd-io handle_ksmbd_work Call Trace: _raw_write_lock+0x74/0xd0 ksmbd_close_fd_app_instance_id+0x183/0x410 smb2_open+0x1346/0x4430 handle_ksmbd_work+0x2bb/0x7b0 Reached from an authenticated session against a share with the default durable-handle and oplock configuration: two sessions open the same file with a durable-v2 handle and an RH lease under distinct AppInstanceIds, both log off, one reconnects with DH2C, and a later durable-v2 create carrying the other AppInstanceId walks into the freed session. Constrain the loop to the oplock owned by the file being reopened.
Title ksmbd: only rebind the reopened file's own oplock on durable reconnect
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

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Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-09-11T19:45:29.551Z

Reserved: 2026-09-11T19:38:34.739Z

Link: CVE-2026-89635

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-11T20:19:49.120

Modified: 2026-09-11T20:19:49.120

Link: CVE-2026-89635

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-12T07:30:10Z

Weaknesses