From nobody Sun Feb 8 04:12:52 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66443EB64DD for ; Fri, 23 Jun 2023 11:14:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231829AbjFWLOV (ORCPT ); Fri, 23 Jun 2023 07:14:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229451AbjFWLOQ (ORCPT ); Fri, 23 Jun 2023 07:14:16 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85F0DB7 for ; Fri, 23 Jun 2023 04:14:15 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 3341021B12; Fri, 23 Jun 2023 11:14:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1687518854; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AYuj5naZGeFE0xaFXho8MoJJxnJ3BHmuLKgH1l9RAc8=; b=qeafabWYCNR+xeqCAO7OzR4ueyvG2NgkXINY4JmKwTLYfTZmHo4hzIJDQ0Gv0bT48yN4HT zMl96mZ2JNNps134yjbi/J0sV/ZGrXOJ9gSHEmY2DnBBO/kb0RlxELe02ayyHOms8EiW3X ybMExMxcjKJy2UuDNSqAN3jIyRP6cJI= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id C79151331F; Fri, 23 Jun 2023 11:14:13 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id CF7kLYV+lWTcFAAAMHmgww (envelope-from ); Fri, 23 Jun 2023 11:14:13 +0000 From: Nikolay Borisov To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, mohocko@suse.com, jslaby@suse.cz, Nikolay Borisov Subject: [PATCH v4 1/6] x86: Introduce ia32_enabled() Date: Fri, 23 Jun 2023 14:14:04 +0300 Message-Id: <20230623111409.3047467-2-nik.borisov@suse.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230623111409.3047467-1-nik.borisov@suse.com> References: <20230623111409.3047467-1-nik.borisov@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" IA32 support on 64bit kernels depends on whether CONFIG_IA32_EMULATION is selected or not. As it is a compile time option it doesn't provide the flexibility to have distributions set their own policy for IA32 support and give the user the flexibility to override it. As a first step introduce ia32_enabled() which abstracts whether IA32 compat is turned on or off. Upcoming patches will implement the ability to set IA32 compat state at boot time. Signed-off-by: Nikolay Borisov --- arch/x86/entry/common.c | 4 ++++ arch/x86/include/asm/ia32.h | 16 +++++++++++++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 6c2826417b33..ef5a154a7413 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -96,6 +96,10 @@ static __always_inline int syscall_32_enter(struct pt_re= gs *regs) return (int)regs->orig_ax; } =20 +#ifdef CONFIG_IA32_EMULATION +bool __ia32_enabled =3D true; +#endif + /* * Invoke a 32-bit syscall. Called with IRQs on in CONTEXT_KERNEL. */ diff --git a/arch/x86/include/asm/ia32.h b/arch/x86/include/asm/ia32.h index fada857f0a1e..5a2ae24b1204 100644 --- a/arch/x86/include/asm/ia32.h +++ b/arch/x86/include/asm/ia32.h @@ -68,6 +68,20 @@ extern void ia32_pick_mmap_layout(struct mm_struct *mm); =20 #endif =20 -#endif /* CONFIG_IA32_EMULATION */ +extern bool __ia32_enabled; + +static inline bool ia32_enabled(void) +{ + return __ia32_enabled; +} + +#else /* !CONFIG_IA32_EMULATION */ + +static inline bool ia32_enabled(void) +{ + return IS_ENABLED(CONFIG_X86_32); +} + +#endif =20 #endif /* _ASM_X86_IA32_H */ --=20 2.34.1 From nobody Sun Feb 8 04:12:52 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12E9FC001B0 for ; Fri, 23 Jun 2023 11:14:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231913AbjFWLO1 (ORCPT ); Fri, 23 Jun 2023 07:14:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54774 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231764AbjFWLOR (ORCPT ); Fri, 23 Jun 2023 07:14:17 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72B96199D for ; Fri, 23 Jun 2023 04:14:16 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id A80811F45E; Fri, 23 Jun 2023 11:14:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1687518854; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EQ/DfJOw6rhJ0Q8RfJ8V8sAvnYjehg1AbCaXsmtUdXc=; b=aT0CMxf//mOxtK2JGQPKVgpvdTBAyDmbfDByK0o1HQicMpOBP454WZ0xknayZaSYAWsfu2 qhROwC4p2hvnzUkvOHibMENz/6ArlnvWCP5E7PabNv8atyRDrq+Ea2khKy4KiZR4GLm6lq Xsh/56BYRkOM0KZln5iXqf9qC9jsrfQ= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 470421331F; Fri, 23 Jun 2023 11:14:14 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id wAB3DoZ+lWTcFAAAMHmgww (envelope-from ); Fri, 23 Jun 2023 11:14:14 +0000 From: Nikolay Borisov To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, mohocko@suse.com, jslaby@suse.cz, Nikolay Borisov Subject: [PATCH v4 2/6] x86/entry: Rename ignore_sysret() Date: Fri, 23 Jun 2023 14:14:05 +0300 Message-Id: <20230623111409.3047467-3-nik.borisov@suse.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230623111409.3047467-1-nik.borisov@suse.com> References: <20230623111409.3047467-1-nik.borisov@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The SYSCALL instruction cannot really be disabled in compatibility mode. The best that can be done is to configure the CSTAR msr to point to a minimal handler. Currently this handler has a rather misleading name - ignore_sysret() as it's not really doing anything with sysret. Give it a more descriptive name. Signed-off-by: Nikolay Borisov --- arch/x86/entry/entry_64.S | 4 ++-- arch/x86/include/asm/processor.h | 2 +- arch/x86/kernel/cpu/common.c | 2 +- 3 files changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index f31e286c2977..ccce0ccd8589 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1519,12 +1519,12 @@ SYM_CODE_END(asm_exc_nmi) * This handles SYSCALL from 32-bit code. There is no way to program * MSRs to fully disable 32-bit SYSCALL. */ -SYM_CODE_START(ignore_sysret) +SYM_CODE_START(entry_SYSCALL32_ignore) UNWIND_HINT_END_OF_STACK ENDBR mov $-ENOSYS, %eax sysretl -SYM_CODE_END(ignore_sysret) +SYM_CODE_END(entry_SYSCALL32_ignore) #endif =20 .pushsection .text, "ax" diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/proces= sor.h index a1e4fa58b357..61c10b4e3e35 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -399,7 +399,7 @@ static inline unsigned long cpu_kernelmode_gs_base(int = cpu) return (unsigned long)per_cpu(fixed_percpu_data.gs_base, cpu); } =20 -extern asmlinkage void ignore_sysret(void); +extern asmlinkage void entry_SYSCALL32_ignore(void); =20 /* Save actual FS/GS selectors and bases to current->thread */ void current_save_fsgs(void); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 80710a68ef7d..b20774181e1a 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2066,7 +2066,7 @@ void syscall_init(void) (unsigned long)(cpu_entry_stack(smp_processor_id()) + 1)); wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat); #else - wrmsrl_cstar((unsigned long)ignore_sysret); + wrmsrl_cstar((unsigned long)entry_SYSCALL32_ignore); wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); --=20 2.34.1 From nobody Sun Feb 8 04:12:52 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA3ACEB64D7 for ; Fri, 23 Jun 2023 11:14:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231882AbjFWLOZ (ORCPT ); Fri, 23 Jun 2023 07:14:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54776 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231346AbjFWLOR (ORCPT ); Fri, 23 Jun 2023 07:14:17 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72D101FF9 for ; Fri, 23 Jun 2023 04:14:16 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 104EC21B15; Fri, 23 Jun 2023 11:14:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1687518855; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=0Yy85zR9fuPHZsIKybiFZXTFB/OLmUVvR9b3i0pMJzE=; b=qDURYg8SdKUS2CeWjKzKeaUE2JWhPqjAqw74ROnCesy7Xrt1T6opu1bv0KCx5b0kJdxR5R n2Nlp6Ku8HJK4DaAXcQeUF5NtHKmx2/kRkAMKtv6RPo3bDgj6TnSfP2oowpVrsImFXoUlB ++4SWHnumHiq1/eR7cbNFbkPSH/LDLY= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id AE9111331F; Fri, 23 Jun 2023 11:14:14 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id EO3pJ4Z+lWTcFAAAMHmgww (envelope-from ); Fri, 23 Jun 2023 11:14:14 +0000 From: Nikolay Borisov To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, mohocko@suse.com, jslaby@suse.cz, Nikolay Borisov Subject: [PATCH v4 3/6] x86/entry: Compile entry_SYSCALL32_ignore() unconditionally Date: Fri, 23 Jun 2023 14:14:06 +0300 Message-Id: <20230623111409.3047467-4-nik.borisov@suse.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230623111409.3047467-1-nik.borisov@suse.com> References: <20230623111409.3047467-1-nik.borisov@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" To limit the IA32 exposure on 64bit kernels while keeping the flexibility for the user to enable it when required, the compile time enable/disable via CONFIG_IA32_EMULATION is not good enough and will be complemented with a kernel command line option. Right now entry_SYSCALL32_ignore() is only compiled when CONFIG_IA32_EMULATION=3Dn, but boot-time enable- / disablement obviously requires it to be unconditionally available. Remove the #ifndef CONFIG_IA32_EMULATION guard. Signed-off-by: Nikolay Borisov --- arch/x86/entry/entry_64.S | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index ccce0ccd8589..7068af44008a 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1514,7 +1514,6 @@ SYM_CODE_START(asm_exc_nmi) iretq SYM_CODE_END(asm_exc_nmi) =20 -#ifndef CONFIG_IA32_EMULATION /* * This handles SYSCALL from 32-bit code. There is no way to program * MSRs to fully disable 32-bit SYSCALL. @@ -1525,7 +1524,6 @@ SYM_CODE_START(entry_SYSCALL32_ignore) mov $-ENOSYS, %eax sysretl SYM_CODE_END(entry_SYSCALL32_ignore) -#endif =20 .pushsection .text, "ax" __FUNC_ALIGN --=20 2.34.1 From nobody Sun Feb 8 04:12:52 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D687EB64DD for ; Fri, 23 Jun 2023 11:14:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231928AbjFWLOa (ORCPT ); Fri, 23 Jun 2023 07:14:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54782 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231767AbjFWLOR (ORCPT ); Fri, 23 Jun 2023 07:14:17 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C65E62101 for ; Fri, 23 Jun 2023 04:14:16 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 770E41F6E6; Fri, 23 Jun 2023 11:14:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1687518855; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=f0VodzPEDQcX9JjZJBEDkNzZARXLsoiBYtSqjF6vfi8=; b=TlbMDcQxYXlK/x5u7ubvCPwPsUHKpUfZI2GFCE+ITXT1GnMRj8C7W0StJCYva9t3+f64O/ Fc6BaA9+wdK3ikB7F0nzb7Lxkn3Fn/eymNPmyTu4Z51VD2wn5JZ63vwZKARBD6R1AOiX+T TdRl3S2TG4GGIFFOhbEqDYmOQs8iEmY= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 220221331F; Fri, 23 Jun 2023 11:14:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id mNOEBYd+lWTcFAAAMHmgww (envelope-from ); Fri, 23 Jun 2023 11:14:15 +0000 From: Nikolay Borisov To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, mohocko@suse.com, jslaby@suse.cz, Nikolay Borisov Subject: [PATCH v4 4/6] x86/elf: Make loading of 32bit processes depend on ia32_enabled() Date: Fri, 23 Jun 2023 14:14:07 +0300 Message-Id: <20230623111409.3047467-5-nik.borisov@suse.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230623111409.3047467-1-nik.borisov@suse.com> References: <20230623111409.3047467-1-nik.borisov@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Major aspect of ia32 emulation is the ability to load 32bit processes. That's currently decided (among others) by compat_elf_check_arch(). Make the macro use ia32_enabled() to decide if IA32 compat is enabled before loading a 32bit process. Signed-off-by: Nikolay Borisov --- arch/x86/include/asm/elf.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 18fd06f7936a..a0234dfd1031 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -7,6 +7,7 @@ */ #include =20 +#include #include #include #include @@ -149,7 +150,7 @@ do { \ ((x)->e_machine =3D=3D EM_X86_64) =20 #define compat_elf_check_arch(x) \ - (elf_check_arch_ia32(x) || \ + ((elf_check_arch_ia32(x) && ia32_enabled()) || \ (IS_ENABLED(CONFIG_X86_X32_ABI) && (x)->e_machine =3D=3D EM_X86_64)) =20 static inline void elf_common_init(struct thread_struct *t, --=20 2.34.1 From nobody Sun Feb 8 04:12:52 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 90635EB64DD for ; Fri, 23 Jun 2023 11:14:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231940AbjFWLOd (ORCPT ); Fri, 23 Jun 2023 07:14:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54788 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231770AbjFWLOS (ORCPT ); Fri, 23 Jun 2023 07:14:18 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 341B310A for ; Fri, 23 Jun 2023 04:14:17 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id DEB8A1F460; Fri, 23 Jun 2023 11:14:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1687518855; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=aLQna3YJFjX1iJFd+SNHQelZENitCxnrAQsbOG2qcHg=; b=u7iPIm86sgf6oSpl6ZWKQB17ZciWaoZGOhEehOF/CjUorTnknsj2+Hs77nHqnF23PvNjO3 +EuvqLgbfH5xFjccrouWQcgTrxeYK2y9K9jwUSvVLWZUHOs0A+Oy42tMBhgIDUZtX/JZbS voyvodtBDl5QUT6m1cxI0FN4zIjUNrw= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 887BF1331F; Fri, 23 Jun 2023 11:14:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id EP+fHod+lWTcFAAAMHmgww (envelope-from ); Fri, 23 Jun 2023 11:14:15 +0000 From: Nikolay Borisov To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, mohocko@suse.com, jslaby@suse.cz, Nikolay Borisov Subject: [PATCH v4 5/6] x86/entry: Make IA32 syscalls' availability depend on ia32_enabled() Date: Fri, 23 Jun 2023 14:14:08 +0300 Message-Id: <20230623111409.3047467-6-nik.borisov@suse.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230623111409.3047467-1-nik.borisov@suse.com> References: <20230623111409.3047467-1-nik.borisov@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Another major aspect of supporting running of 32bit processes is the ability to access 32bit syscalls. Such syscalls can be invoked by using the legacy int 0x80 handler and sysenter/syscall instructions. If IA32 emulation is disabled ensure that each of those 3 distinct mechanisms are also disabled. For int 0x80 a #GP exception would be generated since the respective descriptor is not going to be loaded at all. Invoking sysenter will also result in a #GP since IA32_SYSENTER_CS contains an invalid segment. Finally, syscall instruction cannot really be disabled so it's configured to execute a minimal handler. Signed-off-by: Nikolay Borisov --- arch/x86/include/asm/proto.h | 3 +++ arch/x86/kernel/cpu/common.c | 37 ++++++++++++++++++------------------ arch/x86/kernel/idt.c | 7 +++++++ 3 files changed, 29 insertions(+), 18 deletions(-) diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h index 12ef86b19910..4d84122bd643 100644 --- a/arch/x86/include/asm/proto.h +++ b/arch/x86/include/asm/proto.h @@ -36,6 +36,9 @@ void entry_INT80_compat(void); #ifdef CONFIG_XEN_PV void xen_entry_INT80_compat(void); #endif +#else /* !CONFIG_IA32_EMULATION */ +#define entry_SYSCALL_compat NULL +#define entry_SYSENTER_compat NULL #endif =20 void x86_configure_nx(void); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index b20774181e1a..aafb83d1b3a7 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -59,6 +59,7 @@ #include #include #include +#include #include #include #include @@ -2053,24 +2054,24 @@ void syscall_init(void) wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS); wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64); =20 -#ifdef CONFIG_IA32_EMULATION - wrmsrl_cstar((unsigned long)entry_SYSCALL_compat); - /* - * This only works on Intel CPUs. - * On AMD CPUs these MSRs are 32-bit, CPU truncates MSR_IA32_SYSENTER_EIP. - * This does not cause SYSENTER to jump to the wrong location, because - * AMD doesn't allow SYSENTER in long mode (either 32- or 64-bit). - */ - wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS); - wrmsrl_safe(MSR_IA32_SYSENTER_ESP, - (unsigned long)(cpu_entry_stack(smp_processor_id()) + 1)); - wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat); -#else - wrmsrl_cstar((unsigned long)entry_SYSCALL32_ignore); - wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); - wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); - wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); -#endif + if (ia32_enabled()) { + wrmsrl_cstar((unsigned long)entry_SYSCALL_compat); + /* + * This only works on Intel CPUs. + * On AMD CPUs these MSRs are 32-bit, CPU truncates MSR_IA32_SYSENTER_EI= P. + * This does not cause SYSENTER to jump to the wrong location, because + * AMD doesn't allow SYSENTER in long mode (either 32- or 64-bit). + */ + wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS); + wrmsrl_safe(MSR_IA32_SYSENTER_ESP, + (unsigned long)(cpu_entry_stack(smp_processor_id()) + 1)); + wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat); + } else { + wrmsrl_cstar((unsigned long)entry_SYSCALL32_ignore); + wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); + wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); + wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); + } =20 /* * Flags to clear on syscall; clear as much as possible diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c index a58c6bc1cd68..41f88da58502 100644 --- a/arch/x86/kernel/idt.c +++ b/arch/x86/kernel/idt.c @@ -10,6 +10,7 @@ #include #include #include +#include #include =20 #define DPL0 0x0 @@ -116,6 +117,9 @@ static const __initconst struct idt_data def_idts[] =3D= { #endif =20 SYSG(X86_TRAP_OF, asm_exc_overflow), +}; + +static const struct idt_data ia32_idt[] __initconst =3D { #if defined(CONFIG_IA32_EMULATION) SYSG(IA32_SYSCALL_VECTOR, entry_INT80_compat), #elif defined(CONFIG_X86_32) @@ -226,6 +230,9 @@ void __init idt_setup_early_traps(void) void __init idt_setup_traps(void) { idt_setup_from_table(idt_table, def_idts, ARRAY_SIZE(def_idts), true); + + if (ia32_enabled()) + idt_setup_from_table(idt_table, ia32_idt, ARRAY_SIZE(ia32_idt), true); } =20 #ifdef CONFIG_X86_64 --=20 2.34.1 From nobody Sun Feb 8 04:12:52 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E204CEB64D7 for ; Fri, 23 Jun 2023 11:14:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231966AbjFWLOh (ORCPT ); Fri, 23 Jun 2023 07:14:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54790 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231784AbjFWLOS (ORCPT ); Fri, 23 Jun 2023 07:14:18 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B9C9BB7 for ; Fri, 23 Jun 2023 04:14:17 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 522791F74D; 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Fri, 23 Jun 2023 11:14:15 +0000 From: Nikolay Borisov To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, mohocko@suse.com, jslaby@suse.cz, Nikolay Borisov Subject: [PATCH v4 6/6] x86: Make IA32_EMULATION boot time configurable Date: Fri, 23 Jun 2023 14:14:09 +0300 Message-Id: <20230623111409.3047467-7-nik.borisov@suse.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230623111409.3047467-1-nik.borisov@suse.com> References: <20230623111409.3047467-1-nik.borisov@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Distributions would like to reduce their attack surface as much as possible but at the same time they'd want to retain flexibility to cater to a variety of legacy software. This stems from the conjecture that compat layer is likely rarely tested and could have latent security bugs. Ideally distributions will set their default policy and also give users the ability to override it as appropriate. To enable this use case, introduce CONFIG_IA32_EMULATION_DEFAULT_DISABLED compile time option, which controls whether 32bit processes/syscalls should be allowed or not. This option is aimed mainly at distributions to set their preferred default behavior in their kernels. To allow users to override the distro's policy, introduce the 'ia32_emulati= on' parameter which allows overriding CONFIG_IA32_EMULATION_DEFAULT_DISABLED state at boot time. Signed-off-by: Nikolay Borisov --- Documentation/admin-guide/kernel-parameters.txt | 6 ++++++ arch/x86/Kconfig | 9 +++++++++ arch/x86/entry/common.c | 9 ++++++++- 3 files changed, 23 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 9e5bab29685f..99ff94e963b8 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1865,6 +1865,12 @@ 0 -- machine default 1 -- force brightness inversion =20 + ia32_emulation=3D [X86-64] + Format: + When true, allows loading 32-bit programs and executing 32-bit + syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at + boot time. When false, unconditionally disables IA32 emulation. + icn=3D [HW,ISDN] Format: [,[,[,]]] =20 diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 53bab123a8ee..15f313399ed4 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -3038,6 +3038,15 @@ config IA32_EMULATION 64-bit kernel. You should likely turn this on, unless you're 100% sure that you don't have any 32-bit programs left. =20 +config IA32_EMULATION_DEFAULT_DISABLED + bool "IA32 emulation disabled by default" + default n + depends on IA32_EMULATION + help + Make IA32 emulation disabled by default. This prevents loading 32-bit + processes and access to 32-bit syscalls. If unsure, leave it to its + default value. + config X86_X32_ABI bool "x32 ABI for 64-bit mode" depends on X86_64 diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index ef5a154a7413..b5dd1e226c99 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -19,6 +19,7 @@ #include #include #include +#include =20 #ifdef CONFIG_XEN_PV #include @@ -97,7 +98,13 @@ static __always_inline int syscall_32_enter(struct pt_re= gs *regs) } =20 #ifdef CONFIG_IA32_EMULATION -bool __ia32_enabled =3D true; +bool __ia32_enabled =3D !IS_ENABLED(CONFIG_IA32_EMULATION_DEFAULT_DISABLED= ); + +static int ia32_emulation_override_cmdline(char *arg) +{ + return kstrtobool(arg, &__ia32_enabled); +} +early_param("ia32_emulation", ia32_emulation_override_cmdline); #endif =20 /* --=20 2.34.1