FAILED: patch "[PATCH] KVM: VMX: Don't use vcpu->run->internal.ndata as an array" failed to apply to 5.11-stable tree

FAILED: patch "[PATCH] KVM: VMX: Don't use vcpu->run->internal.ndata as an array" failed to apply to 5.11-stable tree

[gregkh]

The patch below does not apply to the 5.11-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 04c4f2ee3f68c9a4bf1653d15f1a9a435ae33f7a Mon Sep 17 00:00:00 2001
From: Reiji Watanabe <reijiw@google.com>
Date: Tue, 13 Apr 2021 15:47:40 +0000
Subject: [PATCH] KVM: VMX: Don't use vcpu->run->internal.ndata as an array
 index

__vmx_handle_exit() uses vcpu->run->internal.ndata as an index for
an array access.  Since vcpu->run is (can be) mapped to a user address
space with a writer permission, the 'ndata' could be updated by the
user process at anytime (the user process can set it to outside the
bounds of the array).
So, it is not safe that __vmx_handle_exit() uses the 'ndata' that way.

Fixes: 1aa561b1a4c0 ("kvm: x86: Add "last CPU" to some KVM_EXIT information")
Signed-off-by: Reiji Watanabe <reijiw@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Message-Id: <20210413154739.490299-1-reijiw@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 32cf8287d4a7..29b40e092d13 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6027,19 +6027,19 @@ static int __vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 	     exit_reason.basic != EXIT_REASON_PML_FULL &&
 	     exit_reason.basic != EXIT_REASON_APIC_ACCESS &&
 	     exit_reason.basic != EXIT_REASON_TASK_SWITCH)) {
+		int ndata = 3;
+
 		vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 		vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_DELIVERY_EV;
-		vcpu->run->internal.ndata = 3;
 		vcpu->run->internal.data[0] = vectoring_info;
 		vcpu->run->internal.data[1] = exit_reason.full;
 		vcpu->run->internal.data[2] = vcpu->arch.exit_qualification;
 		if (exit_reason.basic == EXIT_REASON_EPT_MISCONFIG) {
-			vcpu->run->internal.ndata++;
-			vcpu->run->internal.data[3] =
+			vcpu->run->internal.data[ndata++] =
 				vmcs_read64(GUEST_PHYSICAL_ADDRESS);
 		}
-		vcpu->run->internal.data[vcpu->run->internal.ndata++] =
-			vcpu->arch.last_vmentry_cpu;
+		vcpu->run->internal.data[ndata++] = vcpu->arch.last_vmentry_cpu;
+		vcpu->run->internal.ndata = ndata;
 		return 0;
 	}
 

Re: FAILED: patch "[PATCH] KVM: VMX: Don't use vcpu->run->internal.ndata as an array" failed to apply to 5.11-stable tree

[Sasha Levin]

On Sun, Apr 18, 2021 at 12:34:36PM +0200, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 5.11-stable tree.
>If someone wants it applied there, or to any other stable or longterm
>tree, then please email the backport, including the original git commit
>id to <stable@vger.kernel.org>.
>
>thanks,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From 04c4f2ee3f68c9a4bf1653d15f1a9a435ae33f7a Mon Sep 17 00:00:00 2001
>From: Reiji Watanabe <reijiw@google.com>
>Date: Tue, 13 Apr 2021 15:47:40 +0000
>Subject: [PATCH] KVM: VMX: Don't use vcpu->run->internal.ndata as an array
> index
>
>__vmx_handle_exit() uses vcpu->run->internal.ndata as an index for
>an array access.  Since vcpu->run is (can be) mapped to a user address
>space with a writer permission, the 'ndata' could be updated by the
>user process at anytime (the user process can set it to outside the
>bounds of the array).
>So, it is not safe that __vmx_handle_exit() uses the 'ndata' that way.
>
>Fixes: 1aa561b1a4c0 ("kvm: x86: Add "last CPU" to some KVM_EXIT information")
>Signed-off-by: Reiji Watanabe <reijiw@google.com>
>Reviewed-by: Jim Mattson <jmattson@google.com>
>Message-Id: <20210413154739.490299-1-reijiw@google.com>
>Cc: stable@vger.kernel.org
>Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

I've resolved this by taking 8e5332402164 ("KVM: VMX: Convert
vcpu_vmx.exit_reason to a union").

-- 
Thanks,
Sasha