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Commit e870c26f authored by Hou Wenlong's avatar Hou Wenlong Committed by Greg Kroah-Hartman
Browse files

KVM: x86/emulator: Defer not-present segment check in __load_segment_descriptor() 



[ Upstream commit ca85f002258fdac3762c57d12d5e6e401b6a41af ]

Per Intel's SDM on the "Instruction Set Reference", when
loading segment descriptor, not-present segment check should
be after all type and privilege checks. But the emulator checks
it first, then #NP is triggered instead of #GP if privilege fails
and segment is not present. Put not-present segment check after
type and privilege checks in __load_segment_descriptor().

Fixes: 38ba30ba (KVM: x86 emulator: Emulate task switch in emulator.c)
Reviewed-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarHou Wenlong <houwenlong.hwl@antgroup.com>
Message-Id: <52573c01d369f506cadcf7233812427cf7db81a7.1644292363.git.houwenlong.hwl@antgroup.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 657b5802

arch/x86/kvm/emulate.c

+9 −5
Original line number Original line Diff line number Diff line
@@ -1669,11 +1669,6 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, 
		goto exception;

		goto exception;

	}

	}





	if (!seg_desc.p) {

		err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR;

		goto exception;

	}



	dpl = seg_desc.dpl;

	dpl = seg_desc.dpl;





	switch (seg) {

	switch (seg) {
@@ -1713,6 +1708,10 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, 
	case VCPU_SREG_TR:

	case VCPU_SREG_TR:

		if (seg_desc.s || (seg_desc.type != 1 && seg_desc.type != 9))

		if (seg_desc.s || (seg_desc.type != 1 && seg_desc.type != 9))

			goto exception;

			goto exception;

		if (!seg_desc.p) {

			err_vec = NP_VECTOR;

			goto exception;

		}

		old_desc = seg_desc;

		old_desc = seg_desc;

		seg_desc.type |= 2; /* busy */

		seg_desc.type |= 2; /* busy */

		ret = ctxt->ops->cmpxchg_emulated(ctxt, desc_addr, &old_desc, &seg_desc,

		ret = ctxt->ops->cmpxchg_emulated(ctxt, desc_addr, &old_desc, &seg_desc,
@@ -1737,6 +1736,11 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, 
		break;

		break;

	}

	}





	if (!seg_desc.p) {

		err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR;

		goto exception;

	}



	if (seg_desc.s) {

	if (seg_desc.s) {

		/* mark segment as accessed */

		/* mark segment as accessed */

		if (!(seg_desc.type & 1)) {

		if (!(seg_desc.type & 1)) {