From 5adcaca0dcbd54f704c8dd7ee2c7c1a1d27235d3 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 18 Nov 2022 10:38:30 +0800 Subject: [PATCH] KVM: x86: Mark TSS busy during LTR emulation _after_ all fault checks stable inclusion from stable-v5.10.137 commit 68ba319b88889b76e0afcb83ee3f9a07d2ae5f1b category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I60PLB Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=68ba319b88889b76e0afcb83ee3f9a07d2ae5f1b -------------------------------- 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@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 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Zheng Zengkai Reviewed-by: Wei Li --- 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 fb2878c58a00..93eb2fbb141f 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1772,16 +1772,6 @@ 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) @@ -1822,6 +1812,15 @@ 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) -- GitLab