CVE-2026-31718
CriticalSummary
A vulnerability has been identified in the Linux kernel related to use-after-free in the __ksmbd_close_fd() function. The issue arises when a durable file handle survives session disconnect, leading to improper management of byte-range locks.
Risk Assessment
This vulnerability may lead to unexpected system errors, including potential memory leaks or crashes of applications using the SMB protocol.
Recommendation
It is recommended to update the Linux kernel to the latest version to mitigate this vulnerability and to monitor the system for any irregularities related to the SMB protocol.
Original NVD description (English source)
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 NU