CVE-2024-36244 Affecting kernel-rt-debug-modules-extra package, versions <0:5.14.0-427.42.1.el9_4

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-modules-extra package and not the kernel-rt-debug-modules-extra package as distributed by AlmaLinux. See How to fix? for AlmaLinux:9 relevant fixed versions and status.

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

net/sched: taprio: extend minimum interval restriction to entire cycle too

It is possible for syzbot to side-step the restriction imposed by the blamed commit in the Fixes: tag, because the taprio UAPI permits a cycle-time different from (and potentially shorter than) the sum of entry intervals.

We need one more restriction, which is that the cycle time itself must be larger than N * ETH_ZLEN bit times, where N is the number of schedule entries. This restriction needs to apply regardless of whether the cycle time came from the user or was the implicit, auto-calculated value, so we move the existing "cycle == 0" check outside the "if "(!new->cycle_time)" branch. This way covers both conditions and scenarios.

Add a selftest which illustrates the issue triggered by syzbot.

• https://errata.almalinux.org/9/ALSA-2024-8617.html
• https://access.redhat.com/security/cve/CVE-2024-36244
• https://access.redhat.com/errata/RHSA-2024:8617
• https://git.kernel.org/stable/c/91f249b01fe490fce11fbb4307952ca8cce78724
• https://git.kernel.org/stable/c/b939d1e04a90248b4cdf417b0969c270ceb992b2
• https://git.kernel.org/stable/c/fb66df20a7201e60f2b13d7f95d031b31a8831d3