| Message ID | 117283244eab58e94d589af58a5f2b245b8c0025.1642669684.git.houwenlong.hwl@antgroup.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86/emulator: Fix wrong checks when loading code segment in emulator | expand |
On Thu, Jan 20, 2022, Hou Wenlong wrote: > 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(). For posterity, KVM doesn't support CALL GATES or TASK GATES, so the "early" #NP check for those is missing. > Fixes: 38ba30ba51a00 (KVM: x86 emulator: Emulate task switch in emulator.c) > Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com> > --- Reviewed-by: Sean Christopherson <seanjc@google.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 166a145fc1e6..864db6fbe8db 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1616,11 +1616,6 @@ 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) { @@ -1660,6 +1655,10 @@ 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, @@ -1684,6 +1683,11 @@ 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)) {
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) Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com> --- arch/x86/kvm/emulate.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) -- 2.31.1