CVE-2026-89652

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

ceph: bound copied dentry name length in NFS export get name

ceph get name() copies the MDS-supplied name into the caller's NAME MAX-sized buffer with memcpy(name, rinfo->dname, rinfo->dname len) and then writes name[rinfo->dname len] = 0, without checking dname len against NAME MAX. A malicious or buggy MDS that returns a LOOKUPNAME reply with dname len > NAME MAX overflows the buffer. get snap name() copies rde->name / rde->name len the same unchecked way.

Impact: a malicious or compromised Ceph MDS overflows the NAME MAX name buffer in a client's NFS-export get name path, a slab out-of-bounds write reported by KASAN. Reachable when a CephFS mount is re-exported over NFS.

Add ceph export copy name(), which rejects lengths above NAME MAX with -ENAMETOOLONG before the copy, and use it in both ceph get name() and get snap name().