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FAILED: patch "[PATCH] KVM: VMX: Don't use vcpu->run->internal.ndata as an array" failed to apply to 5.10-stable tree

PATCH [email protected] 1 participant 1 message Apr 18, 2021

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The patch below does not apply to the 5.10-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 <[email protected]>.

thanks,

greg k-h

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

From 04c4f2ee3f68c9a4bf1653d15f1a9a435ae33f7a Mon Sep 17 00:00:00 2001
From: Reiji Watanabe <[email protected]>
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 <[email protected]>
Reviewed-by Jim Mattson <[email protected]>

Message-Id: <[email protected]>

Cc [email protected]
Signed-off-by Paolo Bonzini <[email protected]>
arch/x86/kvm/vmx/vmx.c +5 -5
index 32cf8287d4a7..29b40e092d13 100644
@@ -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;
 	}