CVE-2026-89495

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

ocfs2: bound namelen in dlm_migrate_request_handler

Patch series "ocfs2/dlm: bound peer-controlled lengths in the o2dlm".

The o2dlm receive handlers trust u8 length and count fields from the wire
without bounding them, so a node in a DLM domain can corrupt or panic any
other node with a malformed message.  Three defects:

  - dlm_migrate_request_handler() passes migrate->namelen unchecked to
    dlm_init_mle(), which memcpy()s it into the 32-byte mname[] of an
    o2dlm_mle slab object: a heap out-of-bounds write of up to ~215
    attacker-controlled bytes.

  - dlm_mig_lockres_handler() passes mres->lockname_len unchecked to
    dlm_init_lockres(), which memcpy()s it into the 32-byte o2dlm_lockname
    slab object: a heap out-of-bounds write of up to ~223 bytes.

  - the same handler trusts mres->num_locks without checking that the
    message is large enough to hold that many entries, so
    dlm_process_recovery_data() walks mres->ml[] past the kmalloc(data_len)
    copy and trips a BUG_ON (an out-of-bounds read ending in a panic).

The other o2dlm receive handlers already reject an oversized name; the
migration and recovery handlers have omitted it since the DLM was added
(see the Fixes tags).  Patch 1 bounds namelen; patch 2 validates
lockname_len, num_locks, and the payload size.  Conforming recovery and
migration traffic is unaffected.

o2net authenticates peers only by the DLM domain key, so any node that has
joined the domain -- including a compromised or malicious member -- can
send these messages.  There is no local trigger; the attacker must already
be a member of the cluster.

Each sink was confirmed under KASAN with an out-of-tree module mirroring
it exactly -- a kmem_cache/kmalloc of the real destination size, then the
same unclamped memcpy/loop: slab-out-of-bounds Write for the two writes,
Read for the recovery walk, and a panic.  A userspace AddressSanitizer
build faults identically under -m32 and -m64.  Scrubbed logs are available
on request.

I reported this privately to security@kernel.org and the ocfs2 maintainers
on 2026-06-20; with no response after the standard embargo period I am
posting the fix publicly.  I have no embargo requirement.


This patch (of 2):

A node receiving a DLM_MIGRATE_REQUEST message trusts the peer-supplied
name length (migrate->namelen) without bounding it.  dlm_init_mle() then
copies that many bytes into the fixed DLM_LOCKID_NAME_MAX-byte mname[]
array of an o2dlm_mle slab object, so a malformed message from a cluster
peer overflows the slab object by up to ~215 bytes: a heap out-of-bounds
write of attacker-controlled data, reachable by any node in the domain.

Reject an oversized name, the way dlm_master_request_handler() and the
other o2dlm receive handlers already do; the migration handler omits the
check entirely.  Conforming messages are unaffected.