Bug 2464490 (CVE-2026-31718) - CVE-2026-31718 kernel: ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger
Summary: CVE-2026-31718 kernel: ksmbd: fix use-after-free in __ksmbd_close_fd() via du...
Keywords:
Status: NEW
Alias: CVE-2026-31718
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
unspecified
unspecified
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-05-01 15:09 UTC by OSIDB Bzimport
Modified: 2026-05-01 20:36 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


Attachments (Terms of Use)

Description OSIDB Bzimport 2026-05-01 15:09:42 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().


Note You need to log in before you can comment on or make changes to this bug.