KVM: let kvm_destroy_vm_debugfs clean up vCPU debugfs directories

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After commit 63d0434 ("KVM: x86: move kvm_create_vcpu_debugfs after
last failure point") we are creating the pre-vCPU debugfs files
after the creation of the vCPU file descriptor.  This makes it
possible for userspace to reach kvm_vcpu_release before
kvm_create_vcpu_debugfs has finished.  The vcpu->debugfs_dentry
then does not have any associated inode anymore, and this causes
a NULL-pointer dereference in debugfs_create_file.

The solution is simply to avoid removing the files; they are
cleaned up when the VM file descriptor is closed (and that must be
after KVM_CREATE_VCPU returns).  We can stop storing the dentry
in struct kvm_vcpu too, because it is not needed anywhere after
kvm_create_vcpu_debugfs returns.

Reported-by: syzbot+705f4401d5a93a59b87d@syzkaller.appspotmail.com
Fixes: 63d0434837 ("KVM: x86: move kvm_create_vcpu_debugfs after last failure point")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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This commit is contained in:

Paolo Bonzini 2020-06-04 15:16:52 +02:00

parent 6929f71e46

commit d56f5136b0

4 changed files with 10 additions and 16 deletions

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5

arch/arm64/kvm/arm.c

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10

arch/x86/kvm/debugfs.c

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3

include/linux/kvm_host.h

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8

virt/kvm/kvm_main.c

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