UBUNTU-CVE-2026-89902: High severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: LoongArch: Avoid preempt count underflow without probe LoongArch uses break 11 for the breakpoint placed after an instruction that Kprobes executes out of line. Since userspace can issue the same break instruction, dobp() can reach kprobesinglestephandler() when there is no current probe. The handler actually returns false in this case, but it first calls preemptenablenoresched(). The corresponding preemptdisable() is done by kprobebreakpointhandler() on a real Kprobe hit, so it has not run here. As a result, an ordinary userspace breakpoint (code 11) underflows the current task's preempt count. This also makes ininterrupt() return true until the task schedules. One visible consequence is the socket cgroup attribution: cgroupskalloc() treats the allocation as interrupt context and assigns the socket to the root cgroup. A socket opened from the SIGTRAP handler can then avoid a BPFCGROUPINETSOCKCREATE policy attached to the task's own cgroup. Return as soon as kproberunning() reports no active probe. The same check has appeared in [PATCH v10 2/4] of the original LoongArch Kprobes series, but was dropped before the feature reached mainline.