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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 14671C2B9F8 for ; Tue, 25 May 2021 15:15:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8B9061249 for ; Tue, 25 May 2021 15:15:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232129AbhEYPRQ (ORCPT ); Tue, 25 May 2021 11:17:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:54534 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232086AbhEYPRE (ORCPT ); Tue, 25 May 2021 11:17:04 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7956D6141B; Tue, 25 May 2021 15:15:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621955734; bh=69yrtpXUSeq6JELDEXRI7j6w/FRp267IP2K39DOOExs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lUkCtvJIN2SdlSsWMul1oJGOc3O4hWXlrEgs2cYL2BnOIyetp21Kco3P95TgWBJPT cy6/5H9Y5DTAZTQ0HWoMVx9DYn296zSuukspRzIXxv8KDnLiM1FeNmuvPJcam+Apu1 0ljv2P3SPfQwWwWMSvCZAWVOyAMQQc5Sv4vYiOcaGu67Tm0hcgEbeVo1vFYQrw9b45 +pI7pIBJYqUQlVwLzmcjohl0KEnno+zPqwjkMEkT5Wf8ivGsaGgBjgMIYDakSVb3tF omPaLy5NT6xBuFeza1EUOMHQ59zzfEuePjwZeaIbV/X0X64Tq7t7mV43P4S/hRx9Kp T1g0j1HZmK3MA== From: Will Deacon To: linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Will Deacon , Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Peter Zijlstra , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , Quentin Perret , Tejun Heo , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , "Rafael J. Wysocki" , Dietmar Eggemann , Daniel Bristot de Oliveira , kernel-team@android.com Subject: [PATCH v7 05/22] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Date: Tue, 25 May 2021 16:14:15 +0100 Message-Id: <20210525151432.16875-6-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210525151432.16875-1-will@kernel.org> References: <20210525151432.16875-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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. Reviewed-by: Catalin Marinas Signed-off-by: Will Deacon --- arch/arm64/kernel/process.c | 19 ++++++++++++++++++- arch/arm64/kernel/signal.c | 26 ++++++++++++++++++++++++++ 2 files changed, 44 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index b4bb67f17a2c..f4a91bf1ce0c 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -527,6 +527,15 @@ 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 (static_branch_unlikely(&arm64_mismatched_32bit_el0)) + set_tsk_thread_flag(next, TIF_NOTIFY_RESUME); +} + static void update_sctlr_el1(u64 sctlr) { /* @@ -568,6 +577,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, ssbs_thread_switch(next); erratum_1418040_thread_switch(prev, next); ptrauth_thread_switch_user(next); + compat_thread_switch(next); /* * Complete any pending TLB or cache maintenance on this CPU in case @@ -633,8 +643,15 @@ 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 (static_branch_unlikely(&arm64_mismatched_32bit_el0)) + set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); + } + current->mm->context.flags = mmflags; ptrauth_thread_init_user(); mte_thread_init_user(); diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 6237486ff6bb..f8192f4ae0b8 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) { @@ -938,6 +951,19 @@ 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) -- 2.31.1.818.g46aad6cb9e-goog