Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in oplock break notification smb2_oplock_break_noti() reads opinfo->conn without any lock and dereferences it after two allocations which may sleep. When the durable handle owning the oplock is disconnected, session_fd_check() clears opinfo->conn and drops its conn reference under ci->m_lock, and the last ksmbd_conn_put() frees the connection. A break triggered by another connection that races with the teardown can then resurrect the freed connection: ksmbd_conn_get() is a plain atomic_inc, and the queued break work later dereferences the stale conn via ksmbd_conn_write(), a use-after-free reachable by any authenticated client holding a durable batch oplock. Thread the caller's inode into the notification path instead of taking a new reference on it. Every caller of oplock_break() already holds a live ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference, in the parent lease break paths) on the inode that owns the break target's oplock list, so ci cannot be freed during the call, and its lock can be taken without dereferencing opinfo->o_fp, which a concurrent close may free. Select and pin the connection under ci->m_lock, the same lock session_fd_check() and ksmbd_reopen_durable_fd() use to update opinfo->conn, so a concurrent detach either loses the race to the clear or keeps the connection alive until the notification work releases it. Transfer the reference to the work item and release it on allocation failures.

Affected versions

Linux: e735dbd489e3ea02be78dba991056fe1138be51e through before c8279ae8df68cce9cd3b785e85f7a86c80a46e78 (git); b003086d76968298f22e7cf62239833b5a3a06b1 through before 8cc98db4fc590e6c7d9db6529320982ee16c5d1d (git); b003086d76968298f22e7cf62239833b5a3a06b1 through before 0e753899627b5e28a9fea8bca98262a6f65a2452 (git); 945a86b21b40fb17183f5b27461baa6f03e2467f (git); 1ff58dcfcab434ebb51649da33774fbb8e1f7b67 (git); 75e33deda658c1ab3a9336cbdb1436536f9b3660 (git); 6.18.36 through before 6.18.51 (semver); 6.6.143 through before 6.7 (semver); 6.12.94 through before 6.13 (semver); 7.0.13 through before 7.1 (semver); 7.1 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.