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List:       kvm
Subject:    [PATCH] kvm: x86: vmx: add checks on guest RIP
From:       Eugene Korenevsky <ekorenevsky () gmail ! com>
Date:       2014-11-29 15:27:26
Message-ID: 20141129152726.GA25370 () gnote
[Download RAW message or body]

Signed-off-by: Eugene Korenevsky <ekorenevsky@gmail.com>
---

Notes:
    This patch adds checks on Guest RIP specified in Intel Software Developer Manual.
    
    The following checks are performed on processors that support Intel 64 architecture:
    - Bits 63:32 must be 0 if the "IA-32e mode guest" VM-entry control is 0 or if
    the L bit (bit 13) in the access-rights field for CS is 0.
    - If the processor supports N < 64 linear-address bits, bits 63:N must be identical
    if the "IA-32e mode guest" VM-entry control is 1 and the L bit in the access-rights
    field for CS is 1. (No check applies if the processor supports 64 linear-address
    bits.)

 arch/x86/kvm/vmx.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 6a951d8..e2da83b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3828,6 +3828,28 @@ static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
 		 (ss.selector & SELECTOR_RPL_MASK));
 }
 
+#ifdef CONFIG_X86_64
+static bool rip_valid(struct kvm_vcpu *vcpu)
+{
+	unsigned long rip;
+	struct kvm_segment cs;
+	bool longmode;
+
+	/* RIP must be canonical in long mode
+	 * Bits 63:32 of RIP must be zero in other processor modes */
+	longmode = false;
+	if (vm_entry_controls_get(to_vmx(vcpu)) & VM_ENTRY_IA32E_MODE) {
+		vmx_get_segment(vcpu, &cs, VCPU_SREG_CS);
+		longmode = (cs.l != 0);
+	}
+	rip = kvm_register_read(vcpu, VCPU_REGS_RIP);
+	if (longmode)
+		return !is_noncanonical_address(rip);
+	else
+		return (rip >> 32) == 0;
+}
+#endif
+
 /*
  * Check if guest state is valid. Returns true if valid, false if
  * not.
@@ -3873,8 +3895,11 @@ static bool guest_state_valid(struct kvm_vcpu *vcpu)
 		if (!ldtr_valid(vcpu))
 			return false;
 	}
+#ifdef CONFIG_X86_64
+	if (!rip_valid(vcpu))
+		return false;
+#endif
 	/* TODO:
-	 * - Add checks on RIP
 	 * - Add checks on RFLAGS
 	 */
 
-- 
2.0.4

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