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From: Will Deacon <will@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Qais Yousef <qais.yousef@arm.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Quentin Perret <qperret@google.com>, Tejun Heo <tj@kernel.org>,
	Li Zefan <lizefan@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	kernel-team@android.com
Subject: [PATCH v6 04/21] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs
Date: Tue, 18 May 2021 10:47:08 +0100	[thread overview]
Message-ID: <20210518094725.7701-5-will@kernel.org> (raw)
In-Reply-To: <20210518094725.7701-1-will@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 <will@kernel.org>
---
 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)
-- 
2.31.1.751.gd2f1c929bd-goog


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  parent reply	other threads:[~2021-05-18  9:54 UTC|newest]

Thread overview: 83+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-18  9:47 [PATCH v6 00/21] Add support for 32-bit tasks on asymmetric AArch32 systems Will Deacon
2021-05-18  9:47 ` [PATCH v6 01/21] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2021-05-21 10:47   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 02/21] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2021-05-21 10:25   ` Catalin Marinas
2021-05-24 12:05     ` Will Deacon
2021-05-24 13:49       ` Catalin Marinas
2021-05-21 10:41   ` Catalin Marinas
2021-05-24 12:09     ` Will Deacon
2021-05-24 13:46       ` Catalin Marinas
2021-05-21 15:22   ` Qais Yousef
2021-05-24 20:21     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 03/21] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2021-05-21 10:47   ` Catalin Marinas
2021-05-18  9:47 ` Will Deacon [this message]
2021-05-21 10:55   ` [PATCH v6 04/21] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 05/21] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2021-05-21 11:00   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 06/21] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Will Deacon
2021-05-21 16:03   ` Peter Zijlstra
2021-05-24 12:17     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 07/21] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2021-05-21 17:39   ` Qais Yousef
2021-05-24 20:21     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 08/21] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon
2021-05-21 16:25   ` Qais Yousef
2021-05-24 21:09     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 09/21] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon
2021-05-18  9:47 ` [PATCH v6 10/21] sched: Introduce task_struct::user_cpus_ptr to track requested affinity Will Deacon
2021-05-18  9:47 ` [PATCH v6 11/21] sched: Split the guts of sched_setaffinity() into a helper function Will Deacon
2021-05-21 16:41   ` Qais Yousef
2021-05-24 21:16     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 12/21] sched: Allow task CPU affinity to be restricted on asymmetric systems Will Deacon
2021-05-21 17:11   ` Qais Yousef
2021-05-24 21:43     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 13/21] sched: Admit forcefully-affined tasks into SCHED_DEADLINE Will Deacon
2021-05-18 10:20   ` Quentin Perret
2021-05-18 10:28     ` Will Deacon
2021-05-18 10:48       ` Quentin Perret
2021-05-18 10:59         ` Will Deacon
2021-05-18 13:19           ` Quentin Perret
2021-05-20  9:13             ` Juri Lelli
2021-05-20 10:16               ` Will Deacon
2021-05-20 10:33                 ` Quentin Perret
2021-05-20 12:38                   ` Juri Lelli
2021-05-20 12:38                   ` Daniel Bristot de Oliveira
2021-05-20 15:06                     ` Dietmar Eggemann
2021-05-20 16:00                       ` Daniel Bristot de Oliveira
2021-05-20 17:55                         ` Dietmar Eggemann
2021-05-20 18:03                           ` Will Deacon
2021-05-21 11:26                             ` Dietmar Eggemann
2021-05-20 18:01                     ` Will Deacon
2021-05-21  5:25                       ` Juri Lelli
2021-05-21  8:15                         ` Quentin Perret
2021-05-21  8:39                           ` Juri Lelli
2021-05-21 10:37                             ` Will Deacon
2021-05-21 11:23                               ` Dietmar Eggemann
2021-05-21 13:02                                 ` Quentin Perret
2021-05-21 14:04                                   ` Juri Lelli
2021-05-21 17:47                                     ` Dietmar Eggemann
2021-05-21 13:00                               ` Daniel Bristot de Oliveira
2021-05-21 13:12                                 ` Quentin Perret
2021-05-24 20:47                                 ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 14/21] freezer: Add frozen_or_skipped() helper function Will Deacon
2021-05-18  9:47 ` [PATCH v6 15/21] sched: Defer wakeup in ttwu() for unschedulable frozen tasks Will Deacon
2021-05-18  9:47 ` [PATCH v6 16/21] arm64: Implement task_cpu_possible_mask() Will Deacon
2021-05-24 14:57   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 17/21] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2021-05-24 15:02   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 18/21] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2021-05-24 15:46   ` Catalin Marinas
2021-05-24 20:32     ` Will Deacon
2021-05-25  9:43       ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 19/21] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2021-05-24 15:47   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 20/21] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2021-05-24 15:47   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 21/21] Documentation: arm64: describe asymmetric 32-bit support Will Deacon
2021-05-21 17:37   ` Qais Yousef
2021-05-24 21:46     ` Will Deacon
2021-05-24 16:22   ` Catalin Marinas
2021-05-21 17:45 ` [PATCH v6 00/21] Add support for 32-bit tasks on asymmetric AArch32 systems Qais Yousef
2021-05-24 22:08   ` Will Deacon

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