From nobody Fri Nov 14 18:06:31 2025 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 1760814594462533.9131341562525; Sat, 18 Oct 2025 12:09:54 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vACHO-0006hT-Fz; Sat, 18 Oct 2025 15:07:51 -0400 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 1vACH7-0006V6-Uz; Sat, 18 Oct 2025 15:07:33 -0400 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 1vACH6-00016E-5s; Sat, 18 Oct 2025 15:07:33 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 3164E15F7A1; Sat, 18 Oct 2025 22:06:59 +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 E38B72F060A; Sat, 18 Oct 2025 22:07:02 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Paolo Bonzini , Michael Tokarev Subject: [Stable-10.1.2 20/23] target/i386: user: do not set up a valid LDT on reset Date: Sat, 18 Oct 2025 22:06:55 +0300 Message-ID: <20251018190702.1178893-9-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_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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: 1760814605159158500 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 ab18de894e..25bbbf70cc 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -8632,7 +8632,11 @@ static void x86_cpu_reset_hold(Object *obj, ResetTyp= e type) =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