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Date: Mon, 11 Jul 2022 23:27:48 +0000 From: Sean Christopherson <seanjc@...gle.com> To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com> Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, syzbot+760a73552f47a8cd0fd9@...kaller.appspotmail.com, Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, Hou Wenlong <houwenlong.hwl@...group.com> Subject: [PATCH 1/3] 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: e37a75a13cda ("KVM: x86: Emulator ignores LDTR/TR extended base on LLDT/LTR") Reported-by: syzbot+760a73552f47a8cd0fd9@...kaller.appspotmail.com Cc: stable@...r.kernel.org Cc: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp> Cc: Hou Wenlong <houwenlong.hwl@...group.com> Signed-off-by: Sean Christopherson <seanjc@...gle.com> --- arch/x86/kvm/emulate.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 39ea9138224c..09e4b67b881f 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) -- 2.37.0.144.g8ac04bfd2-goog
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