This is a note to let you know that I've just added the patch titled
KVM: x86: Mark TSS busy during LTR emulation _after_ all fault checks
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-mark-tss-busy-during-ltr-emulation-_after_-a.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 106b4e61bb8b71d943fd06a2d872af39b5f46544
Author: Sean Christopherson <seanjc@xxxxxxxxxx>
Date: Mon Jul 11 23:27:48 2022 +0000
KVM: x86: Mark TSS busy during LTR emulation _after_ all fault checks
commit ec6e4d863258d4bfb36d48d5e3ef68140234d688 upstream.
Wait to mark the TSS as busy during LTR emulation until after all fault
checks for the LTR have passed. Specifically, don't mark the TSS busy if
the new TSS base is non-canonical.
Opportunistically drop the one-off !seg_desc.PRESENT check for TR as the
only reason for the early check was to avoid marking a !PRESENT TSS as
busy, i.e. the common !PRESENT is now done before setting the busy bit.
Fixes: e37a75a13cda ("KVM: x86: Emulator ignores LDTR/TR extended base on LLDT/LTR")
Reported-by: syzbot+760a73552f47a8cd0fd9@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220711232750.1092012-2-seanjc@xxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 3edafdffa687..2a5a18ca8837 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1713,16 +1713,6 @@ 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,
- sizeof(seg_desc), &ctxt->exception);
- if (ret != X86EMUL_CONTINUE)
- return ret;
break;
case VCPU_SREG_LDTR:
if (seg_desc.s || seg_desc.type != 2)
@@ -1763,6 +1753,15 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
((u64)base3 << 32)))
return emulate_gp(ctxt, 0);
}
+
+ if (seg == VCPU_SREG_TR) {
+ old_desc = seg_desc;
+ seg_desc.type |= 2; /* busy */
+ ret = ctxt->ops->cmpxchg_emulated(ctxt, desc_addr, &old_desc, &seg_desc,
+ sizeof(seg_desc), &ctxt->exception);
+ if (ret != X86EMUL_CONTINUE)
+ return ret;
+ }
load:
ctxt->ops->set_segment(ctxt, selector, &seg_desc, base3, seg);
if (desc)
