From nobody Tue Feb 10 22:18:17 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 17638458187107.318171185496908; Sat, 22 Nov 2025 13:10:18 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vMung-0008Bn-ES; Sat, 22 Nov 2025 16:05:45 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vMunZ-0008BI-Ix; Sat, 22 Nov 2025 16:05:37 -0500 Received: from isrv.corpit.ru ([212.248.84.144]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vMunP-0006Jp-H5; Sat, 22 Nov 2025 16:05:34 -0500 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 30BDE16D2FF; Sun, 23 Nov 2025 00:03:34 +0300 (MSK) Received: from think4mjt.tls.msk.ru (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id D45583223D3; Sun, 23 Nov 2025 00:03:44 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Paolo Bonzini , Michael Tokarev Subject: [Stable-7.2.22 05/25] target/i386: user: do not set up a valid LDT on reset Date: Sat, 22 Nov 2025 23:55:23 +0300 Message-ID: <20251122210344.48374-5-mjt@tls.msk.ru> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=212.248.84.144; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1763845820164018900 Content-Type: text/plain; charset="utf-8" From: Paolo Bonzini In user-mode emulation, QEMU uses the default setting of the LDT base and limit, which places it at the bottom 64K of virtual address space. However, by default there is no LDT at all in Linux processes, and therefore the limit should be 0. This is visible as a NULL pointer dereference in LSL and LAR instructions when they try to read the LDT at an unmapped address. Resolves: #1376 Cc: qemu-stable@nongnu.org Signed-off-by: Paolo Bonzini (cherry picked from commit 58aa1d08bbc406ba3982f32ffb1bef0ff4f8f369) Signed-off-by: Michael Tokarev diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 489ab9cd41..682d71be88 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -5906,7 +5906,11 @@ static void x86_cpu_reset(DeviceState *dev) =20 env->idt.limit =3D 0xffff; env->gdt.limit =3D 0xffff; +#if defined(CONFIG_USER_ONLY) + env->ldt.limit =3D 0; +#else env->ldt.limit =3D 0xffff; +#endif env->ldt.flags =3D DESC_P_MASK | (2 << DESC_TYPE_SHIFT); env->tr.limit =3D 0xffff; env->tr.flags =3D DESC_P_MASK | (11 << DESC_TYPE_SHIFT); --=20 2.47.3