CVE-2025-23141

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

KVM: x86: Acquire SRCU in KVM_GET_MP_STATE to protect guest memory accesses

Acquire a lock on kvm->srcu when userspace is getting MP state to handle a rather extreme edge case where accepting APIC events, i.e. processing pending INIT or SIPI, can trigger accesses to guest memory. If the vCPU is in L2 with INIT and a TRIPLE_FAULT request pending, then getting MP state will trigger a nested VM-Exit by way of ->check_nested_events(), and emuating the nested VM-Exit can access guest memory.

The splat was originally hit by syzkaller on a Google-internal kernel, and reproduced on an upstream kernel by hacking the triple_fault_event_test selftest to stuff a pending INIT, store an MSR on VM-Exit (to generate a memory access on VMX), and do vcpu_mp_state_get() to trigger the scenario.

============================= WARNING: suspicious RCU usage 6.14.0-rc3-b112d356288b-vmx/pi_lockdep_false_pos-lock #3 Not tainted

include/linux/kvm_host.h:1058 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1 1 lock held by triple_fault_ev/1256: #0: ffff88810df5a330 (&vcpu->mutex){+.+.}-{4:4}, at: kvm_vcpu_ioctl+0x8b/0x9a0 [kvm]

stack backtrace: CPU: 11 UID: 1000 PID: 1256 Comm: triple_fault_ev Not tainted 6.14.0-rc3-b112d356288b-vmx #3 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: dump_stack_lvl+0x7f/0x90 lockdep_rcu_suspicious+0x144/0x190 kvm_vcpu_gfn_to_memslot+0x156/0x180 [kvm] kvm_vcpu_read_guest+0x3e/0x90 [kvm] read_and_check_msr_entry+0x2e/0x180 [kvm_intel] __nested_vmx_vmexit+0x550/0xde0 [kvm_intel] kvm_check_nested_events+0x1b/0x30 [kvm] kvm_apic_accept_events+0x33/0x100 [kvm] kvm_arch_vcpu_ioctl_get_mpstate+0x30/0x1d0 [kvm] kvm_vcpu_ioctl+0x33e/0x9a0 [kvm] __x64_sys_ioctl+0x8b/0xb0 do_syscall_64+0x6c/0x170 entry_SYSCALL_64_after_hwframe+0x4b/0x53

Affected Software

References

• https://git.kernel.org/stable/c/0357c8406dfa09430dd9858ebe813feb65524b6e
• https://git.kernel.org/stable/c/592e040572f216d916f465047c8ce4a308fcca44
• https://git.kernel.org/stable/c/7bc5c360375d28ba5ef6298b0d53e735c81d66a1
• https://git.kernel.org/stable/c/8a3df0aa1087a89f5ce55f4aba816bfcb1ecf1be
• https://git.kernel.org/stable/c/ef01cac401f18647d62720cf773d7bb0541827da
• https://git.kernel.org/stable/c/f5cbe725b7477b4cd677be1b86b4e08f90572997