linux-kernel - [PATCH 3.16 367/370] kvm: fix page struct leak in handle

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Message-ID: <lsq.1489146383.472587749@decadent.org.uk>
Date:   Fri, 10 Mar 2017 11:46:23 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Paolo Bonzini" <pbonzini@...hat.com>,
        "Dmitry Vyukov" <dvyukov@...gle.com>
Subject: [PATCH 3.16 367/370] kvm: fix page struct leak in handle_vmon

3.16.42-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Bonzini <pbonzini@...hat.com>

commit 06ce521af9558814b8606c0476c54497cf83a653 upstream.

handle_vmon gets a reference on VMXON region page,
but does not release it. Release the reference.

Found by syzkaller; based on a patch by Dmitry.

Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
[bwh: Backported to 3.16: use skip_emulated_instruction()]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5954,14 +5954,20 @@ static int nested_vmx_check_vmptr(struct
 		}
 
 		page = nested_get_page(vcpu, vmptr);
-		if (page == NULL ||
-		    *(u32 *)kmap(page) != VMCS12_REVISION) {
+		if (page == NULL) {
 			nested_vmx_failInvalid(vcpu);
+			skip_emulated_instruction(vcpu);
+			return 1;
+		}
+		if (*(u32 *)kmap(page) != VMCS12_REVISION) {
 			kunmap(page);
+			nested_release_page_clean(page);
+			nested_vmx_failInvalid(vcpu);
 			skip_emulated_instruction(vcpu);
 			return 1;
 		}
 		kunmap(page);
+		nested_release_page_clean(page);
 		vmx->nested.vmxon_ptr = vmptr;
 		break;
 	case EXIT_REASON_VMCLEAR: