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

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

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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 ]

The Linux kernel CVE team has assigned CVE-2026-89657 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.6 with commit f628d799972799023d32c2542bb2639eb8c4f84e and fixed in 6.12.109 with commit 058ffa81f9440c5b4714685611cf697fd3739ec9
	Issue introduced in 6.6 with commit f628d799972799023d32c2542bb2639eb8c4f84e and fixed in 6.18.50 with commit 2571b35883268a266554e80d368e67fdfea7fb9d
	Issue introduced in 6.6 with commit f628d799972799023d32c2542bb2639eb8c4f84e and fixed in 7.2.4 with commit 201db408872ca12cf09e36bf0f560138c3dcfa1c
	Issue introduced in 6.6 with commit f628d799972799023d32c2542bb2639eb8c4f84e and fixed in 7.3-rc1 with commit 9ec08b7499a62c6d4afa93d36ab47a43fcad57d1

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-89657
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/ceph/osd_client.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	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