Properly unwind VM creation if kvm_create_vm_debugfs() fails. A recent
change to invoke kvm_create_vm_debug() in kvm_create_vm() was led astray
by buggy try_get_module() handling adding by commit
5f6de5cbebee ("KVM:
Prevent module exit until all VMs are freed"). The debugfs error path
effectively inherits the bad error path of try_module_get(), e.g. KVM
leaves the to-be-free VM on vm_list even though KVM appears to do the
right thing by calling module_put() and falling through.
Opportunistically hoist kvm_create_vm_debugfs() above the call to
kvm_arch_post_init_vm() so that the "post-init" arch hook is actually
invoked after the VM is initialized (ignoring kvm_coalesced_mmio_init()
for the moment). x86 is the only non-nop implementation of the post-init
hook, and it doesn't allocate/initialize any objects that are reachable
via debugfs code (spawns a kthread worker for the NX huge page mitigation).
Leave the buggy try_get_module() alone for now, it will be fixed in a
separate commit.
Fixes:
b74ed7a68ec1 ("KVM: Actually create debugfs in kvm_create_vm()")
Reported-by: syzbot+744e173caec2e1627ee0@syzkaller.appspotmail.com
Cc: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Message-Id: <
20220816053937.2477106-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
if (r)
goto out_err_no_mmu_notifier;
+ r = kvm_create_vm_debugfs(kvm, fdname);
+ if (r)
+ goto out_err_no_debugfs;
+
r = kvm_arch_post_init_vm(kvm);
if (r)
- goto out_err_mmu_notifier;
+ goto out_err;
mutex_lock(&kvm_lock);
list_add(&kvm->vm_list, &vm_list);
*/
if (!try_module_get(kvm_chardev_ops.owner)) {
r = -ENODEV;
- goto out_err_mmu_notifier;
- }
-
- r = kvm_create_vm_debugfs(kvm, fdname);
- if (r)
goto out_err;
+ }
return kvm;
out_err:
- module_put(kvm_chardev_ops.owner);
-out_err_mmu_notifier:
+ kvm_destroy_vm_debugfs(kvm);
+out_err_no_debugfs:
#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
if (kvm->mmu_notifier.ops)
mmu_notifier_unregister(&kvm->mmu_notifier, current->mm);