From: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
[ 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: 38ba30ba51a00 (KVM: x86 emulator: Emulate task switch in emulator.c)
Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
Message-Id: <52573c01d369f506cadcf7233812427cf7db81a7.1644292363.git.houwenlong.hwl@xxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 23d3329e1c73..c5f2a72343e3 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1682,11 +1682,6 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
goto exception;
}
- if (!seg_desc.p) {
- err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR;
- goto exception;
- }
-
dpl = seg_desc.dpl;
switch (seg) {
@@ -1726,6 +1721,10 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
case VCPU_SREG_TR:
if (seg_desc.s || (seg_desc.type != 1 && seg_desc.type != 9))
goto exception;
+ if (!seg_desc.p) {
+ err_vec = NP_VECTOR;
+ goto exception;
+ }
old_desc = seg_desc;
seg_desc.type |= 2; /* busy */
ret = ctxt->ops->cmpxchg_emulated(ctxt, desc_addr, &old_desc, &seg_desc,
@@ -1750,6 +1749,11 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
break;
}
+ if (!seg_desc.p) {
+ err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR;
+ goto exception;
+ }
+
if (seg_desc.s) {
/* mark segment as accessed */
if (!(seg_desc.type & 1)) {
--
2.34.1
