Re: [PATCH] KVM: coalesced_mmio: NULLify the pointers before freeing ring page and dev

[Wei Yongjun <yjwei@cn.fujitsu.com>]

Takuya Yoshikawa wrote:
> kvm_coalesced_mmio_init() keeps to hold the addresses of a coalesced mmio
> ring page and dev even after it has freed them.
>
> This may trigger problems, e.g., if we call kvm_coalesced_mmio_free() in
> kvm_destroy_vm() or kvm_vm_ioctl_register_coalesced_mmio() afterward.
>
> This patch avoids such problems by NULLifying the pointers.
>   

After this patch, I think we also need to do some check in
kvm_vcpu_fault() for coalesced_mmio_ring, since the coalesced_mmio
may not be init correctly. This is other issue, so I will send a
new patch for this.

> Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
> ---
>  virt/kvm/coalesced_mmio.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
> index 5169736..11776b7 100644
> --- a/virt/kvm/coalesced_mmio.c
> +++ b/virt/kvm/coalesced_mmio.c
> @@ -119,8 +119,10 @@ int kvm_coalesced_mmio_init(struct kvm *kvm)
>  	return ret;
>  
>  out_free_dev:
> +	kvm->coalesced_mmio_dev = NULL;
>  	kfree(dev);
>  out_free_page:
> +	kvm->coalesced_mmio_ring = NULL;
>  	__free_page(page);
>  out_err:
>  	return ret;
>