CVE-2026-89652ceph: bound copied dentry name length in NFS export get_name

Official description

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().

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/aadfe588ad8032ea99bda259ae7b8d42854f8193
• https://git.kernel.org/stable/c/3cb09301c30909a7935e9de41f98eeb5ef7e4d40
• https://git.kernel.org/stable/c/dff3d84d14142ea43ad61ef5d6b4de05ba16ba42
• https://git.kernel.org/stable/c/a294064e0e0f81ea607b2f019e16888aa1b0a011
• https://git.kernel.org/stable/c/61d9f27b191b838b96b697ce0bfaee39a138243a
• https://git.kernel.org/stable/c/06fb5e623cdc2402d6bb29be94d9beb9a826ffec
• https://git.kernel.org/stable/c/e7c2fd3893a7f7fcd7e8cf0b2c6348bb1e893df6
• https://git.kernel.org/stable/c/eff8013c5a8916613c742ae5a2cc341cb605c0ae