From mboxrd@z Thu Jan 1 00:00:00 1970 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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 B42FCC388F9 for ; Tue, 27 Oct 2020 21:51:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A16222249 for ; Tue, 27 Oct 2020 21:51:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603835495; bh=nU3hgM26iNL5yzEFEmr4JyXLx49XcFjrIm2/XNRCwTM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lgHZ0ynPJqJ0m2xUjF/y2mZMZ98rRXUNOIhRR41sRZuBJhiw+miMjo5I+6elCZn94 nssaX78F/nMyMxMR0jB8jdETzvPLPci+ZHRQjkti92ddMDTH0BtDFgLX2ikYb9uUa6 nszo8fPUFK1Ntoe/jpsCC4yRKfHePsWhE9iz9HoU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2505991AbgJ0Vvf (ORCPT ); Tue, 27 Oct 2020 17:51:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:43160 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730075AbgJ0Vve (ORCPT ); Tue, 27 Oct 2020 17:51:34 -0400 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 098392225E; Tue, 27 Oct 2020 21:51:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603835493; bh=nU3hgM26iNL5yzEFEmr4JyXLx49XcFjrIm2/XNRCwTM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=h1p/YiTfKA4I1zPlc/xkUOdmqbPbFdOBKAKnCXJRvdNzzI4QZnt3w8WKPMks6DGE1 VYdSfzmRB+n1HaAn8L6ThtVPP4NCyCciXCgHmCz/MMQq0jTVRLdkMyXuXhs1m3hMfc 2o713+d9YtU3ETrrCJWaR5RxubBBoX0yULA/6eRU= From: Will Deacon To: linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org, Will Deacon , Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Peter Zijlstra , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , kernel-team@android.com Subject: [PATCH 4/6] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Date: Tue, 27 Oct 2020 21:51:16 +0000 Message-Id: <20201027215118.27003-5-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20201027215118.27003-1-will@kernel.org> References: <20201027215118.27003-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org Scheduling a 32-bit application on a 64-bit-only CPU is a bad idea. Ensure that 32-bit applications always take the slow-path when returning to userspace on a system with mismatched support at EL0, so that we can avoid trying to run on a 64-bit-only CPU and force a SIGKILL instead. Signed-off-by: Will Deacon --- arch/arm64/kernel/process.c | 21 ++++++++++++++++++++- arch/arm64/kernel/signal.c | 26 ++++++++++++++++++++++++++ 2 files changed, 46 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 4784011cecac..c45b5f9dd66b 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -542,6 +542,17 @@ static void erratum_1418040_thread_switch(struct task_struct *prev, write_sysreg(val, cntkctl_el1); } +static void compat_thread_switch(struct task_struct *next) +{ + if (!is_compat_thread(task_thread_info(next))) + return; + + if (!system_has_mismatched_32bit_el0()) + return; + + set_tsk_thread_flag(next, TIF_NOTIFY_RESUME); +} + /* * Thread switching. */ @@ -558,6 +569,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, uao_thread_switch(next); ssbs_thread_switch(next); erratum_1418040_thread_switch(prev, next); + compat_thread_switch(next); /* * Complete any pending TLB or cache maintenance on this CPU in case @@ -620,8 +632,15 @@ unsigned long arch_align_stack(unsigned long sp) */ void arch_setup_new_exec(void) { - current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0; + unsigned long mmflags = 0; + + if (is_compat_task()) { + mmflags = MMCF_AARCH32; + if (system_has_mismatched_32bit_el0()) + set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); + } + current->mm->context.flags = mmflags; ptrauth_thread_init_user(current); if (task_spec_ssb_noexec(current)) { diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index a8184cad8890..bcb6ca2d9a7c 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -911,6 +911,19 @@ static void do_signal(struct pt_regs *regs) restore_saved_sigmask(); } +static bool cpu_affinity_invalid(struct pt_regs *regs) +{ + if (!compat_user_mode(regs)) + return false; + + /* + * We're preemptible, but a reschedule will cause us to check the + * affinity again. + */ + return !cpumask_test_cpu(raw_smp_processor_id(), + system_32bit_el0_cpumask()); +} + asmlinkage void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags) { @@ -948,6 +961,19 @@ asmlinkage void do_notify_resume(struct pt_regs *regs, if (thread_flags & _TIF_NOTIFY_RESUME) { tracehook_notify_resume(regs); rseq_handle_notify_resume(NULL, regs); + + /* + * If we reschedule after checking the affinity + * then we must ensure that TIF_NOTIFY_RESUME + * is set so that we check the affinity again. + * Since tracehook_notify_resume() clears the + * flag, ensure that the compiler doesn't move + * it after the affinity check. + */ + barrier(); + + if (cpu_affinity_invalid(regs)) + force_sig(SIGKILL); } if (thread_flags & _TIF_FOREIGN_FPSTATE) -- 2.29.0.rc2.309.g374f81d7ae-goog