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().
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 9.8
AV:N - ceph_get_name() copies LOOKUPNAME/LSSNAP dentry names from a Ceph MDS reply over TCP, and nfsd reaches that callback via exportfs_decode_fh_raw() when CephFS is re-exported, so a remote MDS (or NFS client against such a gateway) hits the overflow on the network path.
AC:L - A malicious MDS fully controls dname_len and the name bytes. nfsd lookup of a Ceph directory uses d_obtain_alias() then reconnect_path(), which deterministically calls get_name; no race, rare config, or uncontrollable layout is required.
PR:N - No local account or capability on the victim is needed. A compromised or malicious MDS supplies the overflowing name, and on NFS-reexported CephFS any remote NFS client can force LOOKUPNAME by presenting a directory filehandle.
UI:N - Once CephFS is mounted and re-exported over NFS, nfsd directory filehandle resolution automatically issues LOOKUPNAME and copies the MDS reply; no extra victim mount, click, or interactive step is required at exploit time.
S:U - The overflow corrupts kernel stack/memory on the NFS/Ceph client host and does not cross a VM, IOMMU, or other security-authority boundary.
C:H - Unbounded memcpy of MDS-controlled name bytes past the NAME_MAX+1 exportfs buffer is memory corruption that can overwrite adjacent kernel objects and be leveraged for arbitrary disclosure.
I:H - Attacker-controlled length and contents overflow the NAME_MAX+1 stack buffer in exportfs_decode_fh_raw(), enabling an arbitrary write and control-flow hijacking.
A:H - The same out-of-bounds write of a 256-byte name buffer by an MDS-chosen length, reported as a KASAN OOB write, reliably oopses or panics the kernel.
| Attack Vector |
Network |
Scope |
Unchanged |
| Attack Complexity |
Low |
Confidentiality Impact |
High |
| Privileges Required |
None |
Integrity Impact |
High |
| User Interaction |
None |
Availability Impact |
High |
AV:N - ceph_get_name() copies LOOKUPNAME/LSSNAP dentry names from a Ceph MDS reply over TCP, and nfsd reaches that callback via exportfs_decode_fh_raw() when CephFS is re-exported, so a remote MDS (or NFS client against such a gateway) hits the overflow on the network path.
AC:L - A malicious MDS fully controls dname_len and the name bytes. nfsd lookup of a Ceph directory uses d_obtain_alias() then reconnect_path(), which deterministically calls get_name; no race, rare config, or uncontrollable layout is required.
PR:N - No local account or capability on the victim is needed. A compromised or malicious MDS supplies the overflowing name, and on NFS-reexported CephFS any remote NFS client can force LOOKUPNAME by presenting a directory filehandle.
UI:N - Once CephFS is mounted and re-exported over NFS, nfsd directory filehandle resolution automatically issues LOOKUPNAME and copies the MDS reply; no extra victim mount, click, or interactive step is required at exploit time.
S:U - The overflow corrupts kernel stack/memory on the NFS/Ceph client host and does not cross a VM, IOMMU, or other security-authority boundary.
C:H - Unbounded memcpy of MDS-controlled name bytes past the NAME_MAX+1 exportfs buffer is memory corruption that can overwrite adjacent kernel objects and be leveraged for arbitrary disclosure.
I:H - Attacker-controlled length and contents overflow the NAME_MAX+1 stack buffer in exportfs_decode_fh_raw(), enabling an arbitrary write and control-flow hijacking.
A:H - The same out-of-bounds write of a 256-byte name buffer by an MDS-chosen length, reported as a KASAN OOB write, reliably oopses or panics the kernel.
CVSS 3.1