CVE-2022-49296

In the Linux kernel, the following vulnerability has been resolved:

ceph: fix possible deadlock when holding Fwb to get inline_data

1, mount with wsync. 2, create a file with O_RDWR, and the request was sent to mds.0:

ceph_atomic_open()--> ceph_mdsc_do_request(openc) finish_open(file, dentry, ceph_open)--> ceph_open()--> ceph_init_file()--> ceph_init_file_info()--> ceph_uninline_data()--> { ... if (inline_version == 1 || /* initial version, no data */ inline_version == CEPH_INLINE_NONE) goto out_unlock; ... }

The inline_version will be 1, which is the initial version for the new create file. And here the ci->i_inline_version will keep with 1, it's buggy.

3, buffer write to the file immediately:

ceph_write_iter()--> ceph_get_caps(file, need=Fw, want=Fb, ...); generic_perform_write()--> a_ops->write_begin()--> ceph_write_begin()--> netfs_write_begin()--> netfs_begin_read()--> netfs_rreq_submit_slice()--> netfs_read_from_server()--> rreq->netfs_ops->issue_read()--> ceph_netfs_issue_read()--> { ... if (ci->i_inline_version != CEPH_INLINE_NONE && ceph_netfs_issue_op_inline(subreq)) return; ... } ceph_put_cap_refs(ci, Fwb);

The ceph_netfs_issue_op_inline() will send a getattr(Fsr) request to mds.1.

4, then the mds.1 will request the rd lock for CInode::filelock from the auth mds.0, the mds.0 will do the CInode::filelock state transation from excl --> sync, but it need to revoke the Fxwb caps back from the clients.

While the kernel client has aleady held the Fwb caps and waiting for the getattr(Fsr).

It's deadlock!

URL: https://tracker.ceph.com/issues/55377

This vulnerability is rated as Moderate severity rather than Important because exploitation is confined to a local denial of service and depends on a non-default mount configuration. On Red Hat Enterprise Linux systems, the deadlock can only be triggered when a Ceph filesystem is mounted with the synchronous write ("wsync") option. An authenticated local user with write privileges on the mount can cause filesystem operations to hang indefinitely, without enabling privilege escalation or data corruption.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.