Messages in this thread | | | Date | Tue, 16 Aug 2022 17:52:32 +0000 | From | Oliver Upton <> | Subject | Re: [PATCH 1/3] KVM: Properly unwind VM creation if creating debugfs fails |
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On Tue, Aug 16, 2022 at 05:39:35AM +0000, Sean Christopherson wrote: > 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
typo: kvm_create_vm_debugfs()
> 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>
Fun times! Thanks for the fix Sean.
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
-- Best, Oliver
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