Description
In the Linux kernel, the following vulnerability has been resolved:
ceph: cap delegated inode count in ceph_parse_deleg_inos()
ceph_parse_deleg_inos() decodes interval sets of delegated inode numbers
from an MDS create-with-delegation reply. For each set it reads a 64-bit
start and a 64-bit len with ceph_decode_64_safe(), which only validates
that the eight bytes are present in the message, not the value, and then
loops over len while inserting entries into s_delegated_inos.
len is fully attacker controlled. A malicious or compromised MDS can send
one huge interval, many intervals in one reply, duplicate intervals, or
repeated replies that accumulate delegated inodes on the same session.
The original code bounded none of these and could spin the insert loop or
grow the xarray without limit.
Bound both dimensions with a single enforcement point. Track the number
of delegated inodes held by each MDS session in an atomic counter and
grow it only in ceph_insert_deleg_ino(), which uses atomic_add_unless()
to refuse to push the count past CEPH_MAX_DELEG_INOS. Because that helper
is the only place the counter grows, the per-session population can never
exceed the cap, so no separate per-session pre-check is needed. The
counter is decremented when async create consumes a delegated inode or
when an insert fails, incremented when a delegated inode is restored,
initialized with the session xarray, and reset when reconnect destroys
the xarray.
A per-session cap alone still lets one reply spin the insert loop on
duplicate ranges without growing the counter, so also cap the aggregate
interval length accepted from a single reply. Together these bound both
the loop trip count per reply and the xarray population across replies.
The cap is a fixed, client-chosen constant rather than a value derived
from the MDS. mds_client_prealloc_inos is a userspace MDS configuration
option; it is never sent to the kernel client on the wire, and a
server-supplied bound could not be trusted for a defensive limit in any
case. The constant is set well above that option's documented default of
1000 (a generous multiple), so legitimate refill behavior is unaffected
while the CPU and xarray memory a malformed delegation stream can consume
stays bounded.
Impact: a malicious or compromised Ceph MDS can no longer make a client
spin through an unbounded delegated-inode interval or grow one session's
delegated-inode xarray without limit.
ceph: cap delegated inode count in ceph_parse_deleg_inos()
ceph_parse_deleg_inos() decodes interval sets of delegated inode numbers
from an MDS create-with-delegation reply. For each set it reads a 64-bit
start and a 64-bit len with ceph_decode_64_safe(), which only validates
that the eight bytes are present in the message, not the value, and then
loops over len while inserting entries into s_delegated_inos.
len is fully attacker controlled. A malicious or compromised MDS can send
one huge interval, many intervals in one reply, duplicate intervals, or
repeated replies that accumulate delegated inodes on the same session.
The original code bounded none of these and could spin the insert loop or
grow the xarray without limit.
Bound both dimensions with a single enforcement point. Track the number
of delegated inodes held by each MDS session in an atomic counter and
grow it only in ceph_insert_deleg_ino(), which uses atomic_add_unless()
to refuse to push the count past CEPH_MAX_DELEG_INOS. Because that helper
is the only place the counter grows, the per-session population can never
exceed the cap, so no separate per-session pre-check is needed. The
counter is decremented when async create consumes a delegated inode or
when an insert fails, incremented when a delegated inode is restored,
initialized with the session xarray, and reset when reconnect destroys
the xarray.
A per-session cap alone still lets one reply spin the insert loop on
duplicate ranges without growing the counter, so also cap the aggregate
interval length accepted from a single reply. Together these bound both
the loop trip count per reply and the xarray population across replies.
The cap is a fixed, client-chosen constant rather than a value derived
from the MDS. mds_client_prealloc_inos is a userspace MDS configuration
option; it is never sent to the kernel client on the wire, and a
server-supplied bound could not be trusted for a defensive limit in any
case. The constant is set well above that option's documented default of
1000 (a generous multiple), so legitimate refill behavior is unaffected
while the CPU and xarray memory a malformed delegation stream can consume
stays bounded.
Impact: a malicious or compromised Ceph MDS can no longer make a client
spin through an unbounded delegated-inode interval or grow one session's
delegated-inode xarray without limit.
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
||||||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
No advisories yet.
References
History
Sat, 12 Sep 2026 00:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-606 | |
| References |
| |
| Metrics |
threat_severity
|
cvssV3_1
|
Fri, 11 Sep 2026 23:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: ceph: cap delegated inode count in ceph_parse_deleg_inos() ceph_parse_deleg_inos() decodes interval sets of delegated inode numbers from an MDS create-with-delegation reply. For each set it reads a 64-bit start and a 64-bit len with ceph_decode_64_safe(), which only validates that the eight bytes are present in the message, not the value, and then loops over len while inserting entries into s_delegated_inos. len is fully attacker controlled. A malicious or compromised MDS can send one huge interval, many intervals in one reply, duplicate intervals, or repeated replies that accumulate delegated inodes on the same session. The original code bounded none of these and could spin the insert loop or grow the xarray without limit. Bound both dimensions with a single enforcement point. Track the number of delegated inodes held by each MDS session in an atomic counter and grow it only in ceph_insert_deleg_ino(), which uses atomic_add_unless() to refuse to push the count past CEPH_MAX_DELEG_INOS. Because that helper is the only place the counter grows, the per-session population can never exceed the cap, so no separate per-session pre-check is needed. The counter is decremented when async create consumes a delegated inode or when an insert fails, incremented when a delegated inode is restored, initialized with the session xarray, and reset when reconnect destroys the xarray. A per-session cap alone still lets one reply spin the insert loop on duplicate ranges without growing the counter, so also cap the aggregate interval length accepted from a single reply. Together these bound both the loop trip count per reply and the xarray population across replies. The cap is a fixed, client-chosen constant rather than a value derived from the MDS. mds_client_prealloc_inos is a userspace MDS configuration option; it is never sent to the kernel client on the wire, and a server-supplied bound could not be trusted for a defensive limit in any case. The constant is set well above that option's documented default of 1000 (a generous multiple), so legitimate refill behavior is unaffected while the CPU and xarray memory a malformed delegation stream can consume stays bounded. Impact: a malicious or compromised Ceph MDS can no longer make a client spin through an unbounded delegated-inode interval or grow one session's delegated-inode xarray without limit. | |
| Title | ceph: cap delegated inode count in ceph_parse_deleg_inos() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-11T19:45:39.375Z
Reserved: 2026-09-11T19:38:34.742Z
Link: CVE-2026-89648
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-11T20:19:50.760
Modified: 2026-09-11T20:19:50.760
Link: CVE-2026-89648
Redhat
OpenCVE Enrichment
No data.
Weaknesses
-
CWE-606
Unchecked Input for Loop Condition