| Message ID | 5b7188e6388ac9f4567d14eab32db9adf3e00119.1644292363.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 2/8/22 10:34, Hou Wenlong wrote: > Outer-privilege level return is not implemented in emulator, > move the unhandled logic into __load_segment_descriptor to > make it easier to understand why the checks for RET are > incomplete. > > Suggested-by: Sean Christopherson <seanjc@google.com> > Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com> > --- > arch/x86/kvm/emulate.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 37c4213bdcc1..bd91b952eb0a 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -1631,9 +1631,14 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, > if (!(seg_desc.type & 8)) > goto exception; > > - /* RET can never return to an inner privilege level. */ > - if (transfer == X86_TRANSFER_RET && rpl < cpl) > - goto exception; > + if (transfer == X86_TRANSFER_RET) { > + /* RET can never return to an inner privilege level. */ > + if (rpl < cpl) > + goto exception; > + /* Outer-privilege level return is not implemented */ > + if (rpl > cpl) > + return X86EMUL_UNHANDLEABLE; > + } > if (transfer == X86_TRANSFER_RET || transfer == X86_TRANSFER_TASK_SWITCH) { > if (seg_desc.type & 4) { > /* conforming */ > @@ -2228,9 +2233,6 @@ static int em_ret_far(struct x86_emulate_ctxt *ctxt) > rc = emulate_pop(ctxt, &cs, ctxt->op_bytes); > if (rc != X86EMUL_CONTINUE) > return rc; > - /* Outer-privilege level return is not implemented */ > - if (ctxt->mode >= X86EMUL_MODE_PROT16 && (cs & 3) > cpl) > - return X86EMUL_UNHANDLEABLE; > rc = __load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS, cpl, > X86_TRANSFER_RET, > &new_desc); Queued all three, thanks! Paolo
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 37c4213bdcc1..bd91b952eb0a 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1631,9 +1631,14 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, if (!(seg_desc.type & 8)) goto exception; - /* RET can never return to an inner privilege level. */ - if (transfer == X86_TRANSFER_RET && rpl < cpl) - goto exception; + if (transfer == X86_TRANSFER_RET) { + /* RET can never return to an inner privilege level. */ + if (rpl < cpl) + goto exception; + /* Outer-privilege level return is not implemented */ + if (rpl > cpl) + return X86EMUL_UNHANDLEABLE; + } if (transfer == X86_TRANSFER_RET || transfer == X86_TRANSFER_TASK_SWITCH) { if (seg_desc.type & 4) { /* conforming */ @@ -2228,9 +2233,6 @@ static int em_ret_far(struct x86_emulate_ctxt *ctxt) rc = emulate_pop(ctxt, &cs, ctxt->op_bytes); if (rc != X86EMUL_CONTINUE) return rc; - /* Outer-privilege level return is not implemented */ - if (ctxt->mode >= X86EMUL_MODE_PROT16 && (cs & 3) > cpl) - return X86EMUL_UNHANDLEABLE; rc = __load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS, cpl, X86_TRANSFER_RET, &new_desc);
Outer-privilege level return is not implemented in emulator, move the unhandled logic into __load_segment_descriptor to make it easier to understand why the checks for RET are incomplete. Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com> --- arch/x86/kvm/emulate.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)