CVE-2026-89902

/// Technical description

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, do_bp() can reach kprobe_singlestep_handler() when

there is no current probe.

The handler actually returns false in this case, but it first calls

preempt_enable_no_resched(). The corresponding preempt_disable() is done

by kprobe_breakpoint_handler() 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 in_interrupt() return true until the task schedules. One

visible consequence is the socket cgroup attribution: cgroup_sk_alloc()

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

BPF_CGROUP_INET_SOCK_CREATE

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References