CVE-2024-46830

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

KVM: x86: Acquire kvm->srcu when handling KVM_SET_VCPU_EVENTS

Grab kvm->srcu when processing KVM_SET_VCPU_EVENTS, as KVM will forcibly

leave nested VMX/SVM if SMM mode is being toggled, and leaving nested VMX

reads guest memory.

Note, kvm_vcpu_ioctl_x86_set_vcpu_events() can also be called from KVM_RUN

via sync_regs(), which already holds SRCU. I.e. trying to precisely use

kvm_vcpu_srcu_read_lock() around the problematic SMM code would cause

problems. Acquiring SRCU isn't all that expensive, so for simplicity,

grab it unconditionally for KVM_SET_VCPU_EVENTS.

=============================

WARNING: suspicious RCU usage

6.10.0-rc7-332d2c1d713e-next-vm #552 Not tainted

-----------------------------

include/linux/kvm_host.h:1027 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1

1 lock held by repro/1071:

#0: ffff88811e424430 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x7d/0x970 [kvm]

stack backtrace:

CPU: 15 PID: 1071 Comm: repro Not tainted 6.10.0-rc7-332d2c1d713e-next-vm #552

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+0x13f/0x1a0

kvm_vcpu_gfn_to_memslot+0x168/0x190 [kvm]

kvm_vcpu_read_guest+0x3e/0x90 [kvm]

nested_vmx_load_msr+0x6b/0x1d0 [kvm_intel]

load_vmcs12_host_state+0x432/0xb40 [kvm_intel]

vmx_leave_nested+0x30/0x40 [kvm_intel]

kvm_vcpu_ioctl_x86_set_vcpu_events+0x15d/0x2b0 [kvm]

kvm_arch_vcpu_ioctl+0x1107/0x1750 [kvm]

? mark_held_locks+0x49/0x70

? kvm_vcpu_ioctl+0x7d/0x970 [kvm]

? kvm_vcpu_ioctl+0x497/0x970 [kvm]

kvm_vcpu_ioctl+0x497/0x970 [kvm]

? lock_acquire+0xba/0x2d0

? find_held_lock+0x2b/0x80

? do_user_addr_fault+0x40c/0x6f0

? lock_release+0xb7/0x270

__x64_sys_ioctl+0x82/0xb0

do_syscall_64+0x6c/0x170

entry_SYSCALL_64_after_hwframe+0x4b/0x53

RIP: 0033:0x7ff11eb1b539

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