linux-kernel - Re: [PATCH] KVM: nvmx: retry writing guest memory after page fault injected

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <CE1E9880-3812-473F-A38B-2FAC45A95839@oracle.com>
Date:   Thu, 26 Dec 2019 02:20:59 +0200
From:   Liran Alon <liran.alon@...cle.com>
To:     linmiaohe <linmiaohe@...wei.com>
Cc:     pbonzini@...hat.com, rkrcmar@...hat.com,
        sean.j.christopherson@...el.com, vkuznets@...hat.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] KVM: nvmx: retry writing guest memory after page fault
 injected



> On 25 Dec 2019, at 4:21, linmiaohe <linmiaohe@...wei.com> wrote:
> 
> From: Miaohe Lin <linmiaohe@...wei.com>
> 
> We should retry writing guest memory when kvm_write_guest_virt_system()
> failed and page fault is injected in handle_vmread().
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

Patch fix seems correct to me:
Reviewed-by: Liran Alon <liran.alon@...cle.com>

However, I suggest to rephrase commit title & message as follows:

"""
KVM: nVMX: vmread should not set rflags to specify success in case of #PF

In case writing to vmread destination operand result in a #PF, vmread should
not call nested_vmx_succeed() to set rflags to specify success. Similar to as
done in for VMPTRST (See handle_vmptrst()).
"""

In addition, it will be appreciated if you would also submit kvm-unit-test that verifies this condition.

-Liran

> ---
> arch/x86/kvm/vmx/nested.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 8edefdc9c0cb..c1ec9f25a417 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -4799,8 +4799,10 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
> 					instr_info, true, len, &gva))
> 			return 1;
> 		/* _system ok, nested_vmx_check_permission has verified cpl=0 */
> -		if (kvm_write_guest_virt_system(vcpu, gva, &value, len, &e))
> +		if (kvm_write_guest_virt_system(vcpu, gva, &value, len, &e)) {
> 			kvm_inject_page_fault(vcpu, &e);
> +			return 1;
> +		}
> 	}
> 
> 	return nested_vmx_succeed(vcpu);
> -- 
> 2.19.1
>