From nobody Sun Feb 8 07:15:07 2026 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17ED013BAD5 for ; Tue, 23 Jul 2024 23:20:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721776862; cv=none; b=LPXzgPKgNU+CyxpdopI/ZLwe8S+K586w+y6nNQ3NTyoOVXPRZi+XgqiyoR+OhKO3M9j4e1ovHmn0aihcLfycUUiVU1DhHJRZPvKoeYsU8B/i9PnG/SmU1OKW4ww5B3ZV1smqLhY9qGOQt2Z3FQe58P3PZOlpBDCsrkVquu5MYlU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721776862; c=relaxed/simple; bh=8Y+iYHayY2JJwgeVzz2tqt/MVZXDqspYUC9TRMwsdlw=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=tyAaw4YMW9F8C815Kn2in/zBlG2p/AX95bmGeDd5EJxC57S2E0vFbHheqoeMgnQCFKHtf/LgFFZPsUSjhu1VLWJjjy7tcirTCTP3km5zi/yTiKjo7w58ZV0EsCICJYxpH2FkOFYnFChQxsc+pGCgevHhjf62P09BPwBurUqvmk0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=WMj1p28n; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="WMj1p28n" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-7a28217cfecso1132931a12.2 for ; Tue, 23 Jul 2024 16:20:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1721776859; x=1722381659; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:reply-to:from:to:cc :subject:date:message-id:reply-to; bh=ZhkUKgGKAmtJvBC69563aw4qrws1Qh7sTPRPKMZcT4I=; b=WMj1p28nLokCNYDM13AMw9xiLwqoQnA5mw5pcosXr+/804cQzFcSNAAcSId4mkS8CR fRpxgMEtmeIY7+0nxPsZeX1CzSs3DkwJCZ19VvlAUH2sZ+PxG+jufTNqdFMBOg6KVNFF OioRvAs4YEb2yndIl1Yi07WbNSZNHBlSw4QiG63tAo7t8J6rz4ykN4OeFWQQOLJ1RRVj q3I571FYlVZ0c6G1IcxROo3mJQcBqYnj4tjxm+wzVJwiZtgT90jz7w5cG8HO5vaDaJzp VP50wgF/DGzUwvOCTqsR/B0m5gDEhPz6UMtyMyf46HFY80mliX5ic3RCDB6KI4KDoHo3 1HqA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1721776859; x=1722381659; h=cc:to:from:subject:message-id:mime-version:date:reply-to :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=ZhkUKgGKAmtJvBC69563aw4qrws1Qh7sTPRPKMZcT4I=; b=p25xVL9QtuRSa57r6xBRuKAGTmHW6OuFtrRCsEW0QUl68g0HwcNvWObEy3/5Gjoum0 T2kgI0S1I2Wiv+JXHxx/+Dxt64a9aGsuZCWEjQu65HQzHXThrJZmZKfnuZIQicmL16rN CMfKcapMt00eqsvdTCXxUmwGimMe6t9v9dwGRFnyDvHgr5ww2dqX/3qNq/0xQz54hznb RVNxorlaE7Wkgv/rKDtKX2tJ9n7ofTuIuLanLOYI5+RRtRcHAAqKlkUFEXWZ+xg+B9kj lBXhvA0nZEKrCMDpjy1tCkuP5teC5GHlPL4viLQGKmd4qx7a5EeajKPYq9uupvdTxVTp Us+Q== X-Forwarded-Encrypted: i=1; AJvYcCV9sTyrW5c2ZU5UQLkF9aDDWEmvtiQH9gVsupoSDdBsyBDrDblznyOM2vXe4raOulxKw0ay0gkoGBV0XzksRFY4HmJioY+YAGbZ1ZEq X-Gm-Message-State: AOJu0YxBBOh1fyIIDv/QeRvATDf72w+XaVa5zYLY2GmH3kJ/jgK6pV2c DlLh/WyEsP9PXDIV6O8P/Uh/cUAhG1r6gn6xHk3htnF63wyvrZcrix2yE5eqJezHYcfxAKAZ42s +ng== X-Google-Smtp-Source: AGHT+IHW/3mXbfu5Pg9dVenRcl8JGJI1fc7+S8jmzEbKrBTiWqrOQZhFB+0q7F3ISVuCk3mxT07+/UreqNg= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6a02:58c:b0:6f3:b24:6c27 with SMTP id 41be03b00d2f7-7a87dcb0297mr1138a12.5.1721776859071; Tue, 23 Jul 2024 16:20:59 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 23 Jul 2024 16:20:55 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.45.2.1089.g2a221341d9-goog Message-ID: <20240723232055.3643811-1-seanjc@google.com> Subject: [PATCH] KVM: x86: Acquire kvm->srcu when handling KVM_SET_VCPU_EVENTS From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Grab kvm->srcu when processing KVM_SET_VCPU_EVENTS, as KVM will forcibly leave nested VMX/SVM if SMM mode is being toggled, and leaving nested VMX reads guest memory. Note, kvm_vcpu_ioctl_x86_set_vcpu_events() can also be called from KVM_RUN via sync_regs(), which already holds SRCU. I.e. trying to precisely use kvm_vcpu_srcu_read_lock() around the problematic SMM code would cause problems. Acquiring SRCU isn't all that expensive, so for simplicity, grab it unconditionally for KVM_SET_VCPU_EVENTS. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D WARNING: suspicious RCU usage 6.10.0-rc7-332d2c1d713e-next-vm #552 Not tainted ----------------------------- include/linux/kvm_host.h:1027 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active =3D 2, debug_locks =3D 1 1 lock held by repro/1071: #0: ffff88811e424430 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x7d/= 0x970 [kvm] stack backtrace: CPU: 15 PID: 1071 Comm: repro Not tainted 6.10.0-rc7-332d2c1d713e-next-vm = #552 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: dump_stack_lvl+0x7f/0x90 lockdep_rcu_suspicious+0x13f/0x1a0 kvm_vcpu_gfn_to_memslot+0x168/0x190 [kvm] kvm_vcpu_read_guest+0x3e/0x90 [kvm] nested_vmx_load_msr+0x6b/0x1d0 [kvm_intel] load_vmcs12_host_state+0x432/0xb40 [kvm_intel] vmx_leave_nested+0x30/0x40 [kvm_intel] kvm_vcpu_ioctl_x86_set_vcpu_events+0x15d/0x2b0 [kvm] kvm_arch_vcpu_ioctl+0x1107/0x1750 [kvm] ? mark_held_locks+0x49/0x70 ? kvm_vcpu_ioctl+0x7d/0x970 [kvm] ? kvm_vcpu_ioctl+0x497/0x970 [kvm] kvm_vcpu_ioctl+0x497/0x970 [kvm] ? lock_acquire+0xba/0x2d0 ? find_held_lock+0x2b/0x80 ? do_user_addr_fault+0x40c/0x6f0 ? lock_release+0xb7/0x270 __x64_sys_ioctl+0x82/0xb0 do_syscall_64+0x6c/0x170 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7ff11eb1b539 Fixes: f7e570780efc ("KVM: x86: Forcibly leave nested virt when SMM state i= s toggled") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index af6c8cf6a37a..d3a4333807c6 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6042,7 +6042,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp, if (copy_from_user(&events, argp, sizeof(struct kvm_vcpu_events))) break; =20 + kvm_vcpu_srcu_read_lock(vcpu); r =3D kvm_vcpu_ioctl_x86_set_vcpu_events(vcpu, &events); + kvm_vcpu_srcu_read_unlock(vcpu); break; } case KVM_GET_DEBUGREGS: { base-commit: 332d2c1d713e232e163386c35a3ba0c1b90df83f --=20 2.45.2.1089.g2a221341d9-goog