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:

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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

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