Red Hat Bugzilla – Bug 1501878
CVE-2017-15265 kernel: Use-after-free in snd_seq_ioctl_create_port()
Last modified: 2018-08-28 18:23:34 EDT
A use-after-free vulnerability was found at creating and deleting a port via an ioctl on /dev/snd/seq. The snd_seq_create_port() function creates a port object and returns its pointer, but it doesn't take a refcount and can be deleted immediately by another thread. Meanwhile, snd_seq_ioctl_create_port() still calls the function snd_seq_system_client_ev_port_start() with the created port object that is being deleted, which triggers use-after-free. An attacker can race this use for memory corruption or possibly privilege escalation. At the time of writing, the permissions on the device file required a local console user to be issue the ioctl to allow for the exploit to work correctly. Remote users accessing the system via a shell were not granted permissions to issue an IOCTL that can trigger this condition. References: http://seclists.org/oss-sec/2017/q4/58 http://mailman.alsa-project.org/pipermail/alsa-devel/2017-October/126292.html An upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=71105998845fb012937332fe2e806d443c09e026
Created kernel tracking bugs for this issue: Affects: fedora-all [bug 1501880]
https://www.theregister.co.uk/2017/10/15/advanced_linux_sound_architecture_vulnerable_to_privilege_escalation/
Statement: This issue affects the Linux kernel packages as shipped with Red Hat Enterprise Linux 5,6, 7, realtime and MRG-2. Red Hat Enterprise Linux 5 has transitioned to Production phase 3. During the Production 3 Phase, Critical impact Security Advisories (RHSAs) and selected Urgent Priority Bug Fix Advisories (RHBAs) may be released as they become available. The official life cycle policy can be reviewed here: http://redhat.com/rhel/lifecycle Future Linux kernel updates for the respective releases may address this issue.
Mitigation: It is possible to prevent the affected code from being loaded by blacklisting the kernel module snd_seq. Instructions relating to how to blacklist a kernel module are shown here: https://access.redhat.com/solutions/41278 Alternatively a custom permission set can be created by udev, the correct permissions will depend on your use case. Please contact Red Hat customer support for creating a rule set that can minimize flaw exposure.
kernel-4.13.8-300.fc27 has been pushed to the Fedora 27 stable repository. If problems still persist, please make note of it in this bug report.
kernel-4.13.8-100.fc25 has been pushed to the Fedora 25 stable repository. If problems still persist, please make note of it in this bug report.
kernel-4.13.8-200.fc26 has been pushed to the Fedora 26 stable repository. If problems still persist, please make note of it in this bug report.
Got pinged on not making 5.9.z trackers, which are required for els trackers.
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2018:0676 https://access.redhat.com/errata/RHSA-2018:0676
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2018:1062 https://access.redhat.com/errata/RHSA-2018:1062
This issue has been addressed in the following products: Red Hat Enterprise MRG 2 Via RHSA-2018:1170 https://access.redhat.com/errata/RHSA-2018:1170
This issue has been addressed in the following products: Red Hat Enterprise Linux 7.4 Extended Update Support Via RHSA-2018:1130 https://access.redhat.com/errata/RHSA-2018:1130
This issue has been addressed in the following products: Red Hat Enterprise Linux 6 Via RHSA-2018:2390 https://access.redhat.com/errata/RHSA-2018:2390