CVE-2026-80561
CriticalCVSS 9.8Summary
In the Linux kernel, the decode_locker() function in cls_lock_client.c contains three unsafe decode operations that allow a malicious or compromised OSD to trigger slab-out-of-bounds reads. Missing bounds checks before copying the name, an unchecked pointer advance, and an uncapped length value can lead to memory corruption. The fix replaces unsafe operations with safe variants and returns -EINVAL on any bounds violation.
Risk Assessment
A malicious OSD in a multi-tenant Ceph deployment can exploit this vulnerability to read kernel memory beyond the validated buffer, potentially leading to information disclosure or system instability. The vulnerability can be triggered by any kernel client issuing the lock.get_info class method, e.g., during RBD exclusive lock acquisition.
Recommendation
Apply the official Linux kernel patch that fixes decode_locker() immediately and update systems to a patched kernel version. Additionally, limit trust in OSDs and monitor OSD sessions for anomalous behavior.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: libceph: fix multiple unsafe decodes in decode_locker() decode_locker() in cls_lock_client.c contains three unsafe decode operations that allow a malicious or compromised OSD to trigger slab-out-of-bounds reads: 1. ceph_decode_copy() at the locker_id_t name field has no preceding bounds check. With p == end after ceph_start_decoding() accepts struct_len=0, this reads sizeof(ceph_entity_name) = 9 bytes past the validated buffer boundary. 2. *p += sizeof(struct ceph_timespec) after the locker_info_t header is an unchecked pointer advance. A malicious OSD can position p past end, causing all subsequent _safe checks to pass against a bogus boundary. 3. len = ceph_decode_32(p) has no preceding bounds check, and the immediately following *p += len is uncapped. A malicious OSD can send len=0xffffffff, advancing p gigabytes past end and escaping the decode window entirely. Fix all three by replacing bare operations with their safe variants: ceph_decode_copy -> ceph_decode_copy_safe *p += sizeof(...) -> ceph_decode_skip_n ceph_decode_32(p) -> ceph_decode_32_safe *p += len -> ceph_decode_skip_n A new label is added to return -EINVAL on any bounds violation. -EINVAL is appropriate here: the data received from the OSD is structurally malformed, which is an invalid argument to the decode contract regardless of whether the caller or the wire is at fault. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment can trigger this against any kernel client that issues the lock.get_info class method (e.g. during RBD exclusive lock acquisition) without any further privileges beyond OSD session establishment. [ idryomov: use ceph_decode_skip_string() to skip description, trim changelog ]