From patchwork Wed Sep 1 20:30:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 12470263 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61F4CC19F38 for ; Wed, 1 Sep 2021 20:30:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4680B61027 for ; Wed, 1 Sep 2021 20:30:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231549AbhIAUbh (ORCPT ); Wed, 1 Sep 2021 16:31:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231490AbhIAUbg (ORCPT ); Wed, 1 Sep 2021 16:31:36 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 37C93C0613CF for ; Wed, 1 Sep 2021 13:30:39 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id j9-20020a2581490000b02905897d81c63fso698595ybm.8 for ; Wed, 01 Sep 2021 13:30:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=reply-to:date:in-reply-to:message-id:mime-version:references :subject:from:to:cc; bh=kixEwIb9gqW04gwAAeUnH/ecCVyWuRkL9QSYK7iSzQk=; b=vI3cqGN3v2ltfEVTsw8l2uRo5chArr25iXsE02pKsVchqSHX3JFwdJCKj6AY7eXama mND0TI9aNvGKRlJ+u0ATyJo6zfv/z91nwaLKErTznJjazUVaGT690x3Hmpk6XHnLBa+G JH7Io8acVqTGgPK08MIOcCpnPO2aUCiyEmdAi5l4jpwbS0fKi7N0RrQ9sVfanRlND87X hXjn2TmotG9V4F+x55ib2PCSGt8vDrvWR7zm2oYT/36lcg0kO7CFioODoVr/MEbRD7FG AVHD0fYrsuTMVYH20bQZwQJedG/CM2LYbmTU0fBZDFoW11qYPntlj/PQlpJuSqJL+y88 65Hg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:reply-to:date:in-reply-to:message-id :mime-version:references:subject:from:to:cc; bh=kixEwIb9gqW04gwAAeUnH/ecCVyWuRkL9QSYK7iSzQk=; b=IQftK70dGMZuTXKG0PdUCBjJdHiX3nVRWbXkJIKsCJVrx9GEqZ9DR4xPMc/9E4FByI 2drVvfBC0B2b88bD/fA2S3srpaqcT/qAU6EzKnvBGsFJeNJl4hAmFXroCILwF1EyH5/X 43n15vklCwZc3FBjPJUQ7k3f/VUTFTXvKsQZnFgb3A5Z7uqal3WUEbqaN3LmnMzeVmwV JzJ63MhgzJtkw3EKbtZ+WnKcWbwkFhQ+nHZyIk2rkEmTnJJJ58W1AKFg1d0XUNe3hh1a OxCE+K+8jOvtVazAXsQ4HF+ImJScBtYWuHF2CsrKPlegBjA1dBd0GzSp34547WNktPQW HFng== X-Gm-Message-State: AOAM531/44C258UAoaKhre3Bbr/F4MF/4DDdN1ZdjQuAzVUK+W9u1wIv Cm6SrGM6rNoJkHvfix/CglebHgsufQI= X-Google-Smtp-Source: ABdhPJxOy0/3eJr4hrzQ/lo98CzNq7Zzsb3SLqOc/F5UhI3VQK6ru+OrtaCwLB3GIsnL+0WVfa3UVtPABkI= X-Received: from seanjc798194.pdx.corp.google.com ([2620:15c:90:200:9935:5a5e:c7b6:e649]) (user=seanjc job=sendgmr) by 2002:a25:9c01:: with SMTP id c1mr1791237ybo.228.1630528238358; Wed, 01 Sep 2021 13:30:38 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 1 Sep 2021 13:30:26 -0700 In-Reply-To: <20210901203030.1292304-1-seanjc@google.com> Message-Id: <20210901203030.1292304-2-seanjc@google.com> Mime-Version: 1.0 References: <20210901203030.1292304-1-seanjc@google.com> X-Mailer: git-send-email 2.33.0.153.gba50c8fa24-goog Subject: [PATCH v3 1/5] KVM: rseq: Update rseq when processing NOTIFY_RESUME on xfer to KVM guest From: Sean Christopherson To: Russell King , Catalin Marinas , Will Deacon , Guo Ren , Thomas Bogendoerfer , Michael Ellerman , Steven Rostedt , Ingo Molnar , Oleg Nesterov , Thomas Gleixner , Peter Zijlstra , Andy Lutomirski , Mathieu Desnoyers , "Paul E. McKenney" , Boqun Feng , Paolo Bonzini , Shuah Khan Cc: Benjamin Herrenschmidt , Paul Mackerras , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-csky@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, Peter Foley , Shakeel Butt , Sean Christopherson , Ben Gardon Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Invoke rseq's NOTIFY_RESUME handler when processing the flag prior to transferring to a KVM guest, which is roughly equivalent to an exit to userspace and processes many of the same pending actions. While the task cannot be in an rseq critical section as the KVM path is reachable only by via ioctl(KVM_RUN), the side effects that apply to rseq outside of a critical section still apply, e.g. the current CPU needs to be updated if the task is migrated. Clearing TIF_NOTIFY_RESUME without informing rseq can lead to segfaults and other badness in userspace VMMs that use rseq in combination with KVM, e.g. due to the CPU ID being stale after task migration. Fixes: 72c3c0fe54a3 ("x86/kvm: Use generic xfer to guest work function") Reported-by: Peter Foley Bisected-by: Doug Evans Acked-by: Mathieu Desnoyers Cc: Shakeel Butt Cc: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson --- kernel/entry/kvm.c | 4 +++- kernel/rseq.c | 14 +++++++++++--- 2 files changed, 14 insertions(+), 4 deletions(-) diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c index 49972ee99aff..049fd06b4c3d 100644 --- a/kernel/entry/kvm.c +++ b/kernel/entry/kvm.c @@ -19,8 +19,10 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work) if (ti_work & _TIF_NEED_RESCHED) schedule(); - if (ti_work & _TIF_NOTIFY_RESUME) + if (ti_work & _TIF_NOTIFY_RESUME) { tracehook_notify_resume(NULL); + rseq_handle_notify_resume(NULL, NULL); + } ret = arch_xfer_to_guest_mode_handle_work(vcpu, ti_work); if (ret) diff --git a/kernel/rseq.c b/kernel/rseq.c index 35f7bd0fced0..6d45ac3dae7f 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -282,9 +282,17 @@ void __rseq_handle_notify_resume(struct ksignal *ksig, struct pt_regs *regs) if (unlikely(t->flags & PF_EXITING)) return; - ret = rseq_ip_fixup(regs); - if (unlikely(ret < 0)) - goto error; + + /* + * regs is NULL if and only if the caller is in a syscall path. Skip + * fixup and leave rseq_cs as is so that rseq_sycall() will detect and + * kill a misbehaving userspace on debug kernels. + */ + if (regs) { + ret = rseq_ip_fixup(regs); + if (unlikely(ret < 0)) + goto error; + } if (unlikely(rseq_update_cpu_id(t))) goto error; return;