5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Bryam Vargas <redacted>
commit ea5b5609305a8437bc955a0834a530c12246d78f upstream.
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.
Link: https://lore.kernel.org/20260629-b4-disp-94fb6521-v1-0-6953bcc0421f@proton.me (local)
Link: https://lore.kernel.org/20260629-b4-disp-94fb6521-v1-1-6953bcc0421f@proton.me (local)
Fixes: 6714d8e86bf4 ("[PATCH] OCFS2: The Second Oracle Cluster Filesystem")
Signed-off-by: Bryam Vargas <redacted>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Changwei Ge <redacted>
Cc: Heming Zhao <heming.zhao@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Jun Piao <redacted>
Cc: Junxiao Bi <redacted>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ocfs2/dlm/dlmmaster.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -3112,6 +3112,12 @@ int dlm_migrate_request_handler(struct o
name = migrate->name;
namelen = migrate->namelen;
+ if (namelen > DLM_LOCKID_NAME_MAX) {
+ mlog(ML_ERROR, "%s: invalid name length %u in migrate request\n",
+ dlm->name, namelen);
+ ret = -EINVAL;
+ goto leave;
+ }
hash = dlm_lockid_hash(name, namelen);
/* preallocate.. if this fails, abort */