CVE-2017-12190

The bio_map_user_iov and bio_unmap_user functions in block/bio.c in the Linux kernel before 4.13.8 do unbalanced refcounting when a SCSI I/O vector has small consecutive buffers belonging to the same page. The bio_add_pc_page function merges them into one, but the page reference is never dropped. This causes a memory leak and possible system lockup (exploitable against the host OS by a guest OS user, if a SCSI disk is passed through to a virtual machine) due to an out-of-memory condition.

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://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=2b04e8f6bbb196cab4b232af0f8d48ff2c7a8058
• http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=95d78c28b5a85bacbc29b8dba7c04babb9b0d467
• http://seclists.org/oss-sec/2017/q4/52
• http://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.13.8
• http://www.securityfocus.com/bid/101911
• https://access.redhat.com/errata/RHSA-2018:0654
• https://access.redhat.com/errata/RHSA-2018:0676
• https://access.redhat.com/errata/RHSA-2018:1062
• https://access.redhat.com/errata/RHSA-2018:1854
• https://access.redhat.com/errata/RHSA-2019:1170
• https://access.redhat.com/errata/RHSA-2019:1190
• https://bugzilla.redhat.com/show_bug.cgi?id=1495089
• https://github.com/torvalds/linux/commit/2b04e8f6bbb196cab4b232af0f8d48ff2c7a8058
• https://github.com/torvalds/linux/commit/95d78c28b5a85bacbc29b8dba7c04babb9b0d467
• https://lists.debian.org/debian-lts-announce/2017/12/msg00004.html
• https://support.f5.com/csp/article/K93472064?utm_source=f5support\u0026amp%3Butm_medium=RSS
• https://usn.ubuntu.com/3582-1/
• https://usn.ubuntu.com/3582-2/
• https://usn.ubuntu.com/3583-1/
• https://usn.ubuntu.com/3583-2/
• http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=2b04e8f6bbb196cab4b232af0f8d48ff2c7a8058
• http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=95d78c28b5a85bacbc29b8dba7c04babb9b0d467
• http://seclists.org/oss-sec/2017/q4/52
• http://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.13.8
• http://www.securityfocus.com/bid/101911
• https://access.redhat.com/errata/RHSA-2018:0654
• https://access.redhat.com/errata/RHSA-2018:0676
• https://access.redhat.com/errata/RHSA-2018:1062
• https://access.redhat.com/errata/RHSA-2018:1854
• https://access.redhat.com/errata/RHSA-2019:1170
• https://access.redhat.com/errata/RHSA-2019:1190
• https://bugzilla.redhat.com/show_bug.cgi?id=1495089
• https://github.com/torvalds/linux/commit/2b04e8f6bbb196cab4b232af0f8d48ff2c7a8058
• https://github.com/torvalds/linux/commit/95d78c28b5a85bacbc29b8dba7c04babb9b0d467
• https://lists.debian.org/debian-lts-announce/2017/12/msg00004.html
• https://support.f5.com/csp/article/K93472064?utm_source=f5support\u0026amp%3Butm_medium=RSS
• https://usn.ubuntu.com/3582-1/
• https://usn.ubuntu.com/3582-2/
• https://usn.ubuntu.com/3583-1/
• https://usn.ubuntu.com/3583-2/