From: Sean Christopherson Date: Mon, 11 Jul 2022 23:27:48 +0000 (+0000) Subject: KVM: x86: Mark TSS busy during LTR emulation _after_ all fault checks X-Git-Tag: baikal/mips/sdk6.1~5143^2~6^2~93 X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=1b81d1d45d06fa54fbc50e109335741b1a547c19;p=kernel.git KVM: x86: Mark TSS busy during LTR emulation _after_ all fault checks 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: 2268660cef03 ("KVM: x86: Emulator ignores LDTR/TR extended base on LLDT/LTR") Reported-by: syzbot+760a73552f47a8cd0fd9@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Cc: Tetsuo Handa Cc: Hou Wenlong Signed-off-by: Sean Christopherson Reviewed-by: Maxim Levitsky Link: https://lore.kernel.org/r/20220711232750.1092012-2-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 39ea9138224c6..09e4b67b881fc 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1699,16 +1699,6 @@ 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) @@ -1749,6 +1739,15 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, ((u64)base3 << 32), ctxt)) 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)