CVE-2026-23189

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ceph: fix NULL pointer dereference in ceph_mds_auth_match()<br /> <br /> The CephFS kernel client has regression starting from 6.18-rc1.<br /> We have issue in ceph_mds_auth_match() if fs_name == NULL:<br /> <br /> const char fs_name = mdsc-&gt;fsc-&gt;mount_options-&gt;mds_namespace;<br /> ...<br /> if (auth-&gt;match.fs_name &amp;&amp; strcmp(auth-&gt;match.fs_name, fs_name)) {<br /> / fsname mismatch, try next one */<br /> return 0;<br /> }<br /> <br /> Patrick Donnelly suggested that: In summary, we should definitely start<br /> decoding `fs_name` from the MDSMap and do strict authorizations checks<br /> against it. Note that the `-o mds_namespace=foo` should only be used for<br /> selecting the file system to mount and nothing else. It&amp;#39;s possible<br /> no mds_namespace is specified but the kernel will mount the only<br /> file system that exists which may have name "foo".<br /> <br /> This patch reworks ceph_mdsmap_decode() and namespace_equals() with<br /> the goal of supporting the suggested concept. Now struct ceph_mdsmap<br /> contains m_fs_name field that receives copy of extracted FS name<br /> by ceph_extract_encoded_string(). For the case of "old" CephFS file<br /> systems, it is used "cephfs" name.<br /> <br /> [ idryomov: replace redundant %*pE with %s in ceph_mdsmap_decode(),<br /> get rid of a series of strlen() calls in ceph_namespace_match(),<br /> drop changes to namespace_equals() body to avoid treating empty<br /> mds_namespace as equal, drop changes to ceph_mdsc_handle_fsmap()<br /> as namespace_equals() isn&amp;#39;t an equivalent substitution there ]