CVE-2026-89657libceph: validate OSD extent maps before cursor advance

Official description

In the Linux kernel, the following vulnerability has been resolved: libceph: validate OSD extent maps before cursor advance net/ceph/osd_client.c:osd_sparse_read() validates that the sparse-read data length matches the summed extent lengths, but it does not validate that each OSD-supplied extent is monotonic and lies inside the original request range. A malformed authenticated OSD reply can advertise a far-forward nonzero extent offset with a matching data length and make the client advance the message-data cursor beyond the request buffer. This reaches the BUG_ON(!*length) assertion in ceph_msg_data_next() from the client receive path. Impact: A malicious or compromised authenticated Ceph OSD peer can crash a kernel Ceph client via a malformed sparse-read reply. Reject sparse extent maps that overflow, move backwards, overlap, or extend outside the original sparse-read request before advancing the cursor. [ idryomov: perform sparse_extent_map_valid() check a bit earlier, in CEPH_SPARSE_READ_DATA_LEN instead of CEPH_SPARSE_READ_DATA_PRE state ]

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/94ae5145c520618802b0a24c047dcd5f05835db8
• https://git.kernel.org/stable/c/058ffa81f9440c5b4714685611cf697fd3739ec9
• https://git.kernel.org/stable/c/2571b35883268a266554e80d368e67fdfea7fb9d
• https://git.kernel.org/stable/c/201db408872ca12cf09e36bf0f560138c3dcfa1c
• https://git.kernel.org/stable/c/9ec08b7499a62c6d4afa93d36ab47a43fcad57d1