CVE-2019-15538

An issue was discovered in xfs_setattr_nonsize in fs/xfs/xfs_iops.c in the Linux kernel through 5.2.9. XFS partially wedges when a chgrp fails on account of being out of disk quota. xfs_setattr_nonsize is failing to unlock the ILOCK after the xfs_qm_vop_chown_reserve call fails. This is primarily a local DoS attack vector, but it might result as well in remote DoS if the XFS filesystem is exported for instance via NFS.

Weakness

The product does not properly control the allocation and maintenance of a limited resource.

Affected Software

Potential Mitigations

• Mitigation of resource exhaustion attacks requires that the target system either:

• The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.

• The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/147.html
• https://cwe.mitre.org/data/definitions/227.html
• https://cwe.mitre.org/data/definitions/492.html

References

• http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00064.html
• http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00066.html
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1fb254aa983bf190cfd685d40c64a480a9bafaee
• https://github.com/torvalds/linux/commit/1fb254aa983bf190cfd685d40c64a480a9bafaee
• https://lists.debian.org/debian-lts-announce/2019/09/msg00014.html
• https://lists.debian.org/debian-lts-announce/2019/09/msg00015.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/O3RUDQJXRJQVGHCGR4YZWTQ3ECBI7TXH/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T4JZ6AEUKFWBHQAROGMQARJ274PQP2QP/
• https://lore.kernel.org/linux-xfs/20190823035528.GH1037422%40magnolia/
• https://lore.kernel.org/linux-xfs/20190823192433.GA8736%40eldamar.local
• https://security.netapp.com/advisory/ntap-20191004-0001/
• https://support.f5.com/csp/article/K32592426?utm_source=f5support\u0026amp%3Butm_medium=RSS
• https://usn.ubuntu.com/4144-1/
• https://usn.ubuntu.com/4147-1/
• http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00064.html
• http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00066.html
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1fb254aa983bf190cfd685d40c64a480a9bafaee
• https://github.com/torvalds/linux/commit/1fb254aa983bf190cfd685d40c64a480a9bafaee
• https://lists.debian.org/debian-lts-announce/2019/09/msg00014.html
• https://lists.debian.org/debian-lts-announce/2019/09/msg00015.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/O3RUDQJXRJQVGHCGR4YZWTQ3ECBI7TXH/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T4JZ6AEUKFWBHQAROGMQARJ274PQP2QP/
• https://lore.kernel.org/linux-xfs/20190823035528.GH1037422%40magnolia/
• https://lore.kernel.org/linux-xfs/20190823192433.GA8736%40eldamar.local
• https://security.netapp.com/advisory/ntap-20191004-0001/
• https://support.f5.com/csp/article/K32592426?utm_source=f5support\u0026amp%3Butm_medium=RSS
• https://usn.ubuntu.com/4144-1/
• https://usn.ubuntu.com/4147-1/