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CriticalFix available

ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger When a durable file handle survives session disconnect (TCP close without SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the handle for later reconnection. However, it did not clean up the byte-range locks on fp->lock_list. Later, when the durable scavenger thread times out and calls __ksmbd_close_fd(NULL, fp), the lock cleanup loop did: spin_lock(&fp->conn->llist_lock); This caused a slab use-after-free because fp->conn was NULL and the original connection object had already been freed by ksmbd_tcp_disconnect(). The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were left dangling on the freed conn->lock_list while fp->conn was nulled out. To fix this issue properly, we need to handle the lifetime of smb_lock->clist across three paths: - Safely skip clist deletion when list is empty and fp->conn is NULL. - Remove the lock from the old connection's lock_list in session_fd_check() - Re-add the lock to the new connection's lock_list in ksmbd_reopen_durable_fd().

Products
Kernel
Affected versions
Not specified
Fixed versions
6.12.84, 6.18.25, 6.6.140, 7.0.2
CVEs
CVE-2026-31718
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 03:34 UTC · Revision 1

Source evidence

ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger

core-osv · Original source

Published 1 May 2026, 13:56 UTC

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger When a durable file handle survives session disconnect (TCP close without SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the handle for later reconnection. However, it did not clean up the byte-range locks on fp->lock_list. Later, when the durable scavenger thread times out and calls __ksmbd_close_fd(NULL, fp), the lock cleanup loop did: spin_lock(&fp->conn->llist_lock); This caused a slab use-after-free because fp->conn was NULL and the original connection object had already been freed by ksmbd_tcp_disconnect(). The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were left dangling on the freed conn->lock_list while fp->conn was nulled out. To fix this issue properly, we need to handle the lifetime of smb_lock->clist across three paths: - Safely skip clist deletion when list is empty and fp->conn is NULL. - Remove the lock from the old connection's lock_list in session_fd_check() - Re-add the lock to the new connection's lock_list in ksmbd_reopen_durable_fd().

osv:CVE-2026-31718

Kernel

Fixed versions: 6.6.140, 6.12.84, 6.18.25, 7.0.2

Complete source record
{
  "id": "d248ead70ce2f04d54c3a4f8a2b88a7c94d7683f63016b7f5839e772761263bc",
  "url": "https://osv.dev/vulnerability/CVE-2026-31718",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger When a durable file handle survives session disconnect (TCP close without SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the handle for later reconnection. However, it did not clean up the byte-range locks on fp->lock_list. Later, when the durable scavenger thread times out and calls __ksmbd_close_fd(NULL, fp), the lock cleanup loop did: spin_lock(&fp->conn->llist_lock); This caused a slab use-after-free because fp->conn was NULL and the original connection object had already been freed by ksmbd_tcp_disconnect(). The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were left dangling on the freed conn->lock_list while fp->conn was nulled out. To fix this issue properly, we need to handle the lifetime of smb_lock->clist across three paths: - Safely skip clist deletion when list is empty and fp->conn is NULL. - Remove the lock from the old connection's lock_list in session_fd_check() - Re-add the lock to the new connection's lock_list in ksmbd_reopen_durable_fd().",
    "evidence": "osv:CVE-2026-31718",
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      ],
      "modified": "2026-10-28T02:30:49.671886235Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0000a7780e0e446a28a273572f6ea8f7f582f694",
        "https://git.kernel.org/stable/c/235e32320a470fcd3998fb3774f2290a0eb302a1",
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      "provider_metadata": {
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  "source_id": "core-osv",
  "document_id": 517795,
  "published_at": "2026-05-01T13:56:12.68+00:00"
}