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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3FABDC433EF for ; Sat, 9 Oct 2021 10:08:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2506660E95 for ; Sat, 9 Oct 2021 10:08:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244938AbhJIKKb (ORCPT ); Sat, 9 Oct 2021 06:10:31 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:49554 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244771AbhJIKJc (ORCPT ); Sat, 9 Oct 2021 06:09:32 -0400 Date: Sat, 09 Oct 2021 10:07:33 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1633774054; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=o6n0Pya48OlRRigxij+h92kl6GKG9e7BXeiOnWE+ZGY=; b=N06Scu/Q0tP1oaikQ7WQwNIXOacfXN8e6VmjkRUoeotSNAwDNtvCCT4vaYTE0Fum/+qmeD b+aMlkxNG8fHoPpdLMauDUi6YDWOze99q7EujJngEcp1Wk13rXABUHfThehwhyCNTKnI3j 0pUUBLYvASUmkncpdtr6NsWN6ZoPZbC/bavCGbQuvUK/eGTipFVAU/d97axks819yaYJo1 vGmP5Z+zqAB52P7vuLjSj7IV+Obw5qObK6e+H6QPxkrtQha2vYpCJlcwFQLJsEYUjYVEuX tJFszgpbGSZ1zaAPPJy1K2ZY1FrQHlxFyGMm1YCz4v0xVJs/25C87+d696xY4g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1633774054; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=o6n0Pya48OlRRigxij+h92kl6GKG9e7BXeiOnWE+ZGY=; b=kb8kXwezy3hMOzVhjh18aZ7GuNFjVwbY33z0T5Nguz6wBBZOWAqhazMXW3F9yhHzo0VmdM 1s6RuWtvhgXbh+BA== From: "tip-bot2 for Zhang Qiao" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] kernel/sched: Fix sched_fork() access an invalid sched_task_group Cc: Zhang Qiao , "Peter Zijlstra (Intel)" , Tejun Heo , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210915064030.2231-1-zhangqiao22@huawei.com> References: <20210915064030.2231-1-zhangqiao22@huawei.com> MIME-Version: 1.0 Message-ID: <163377405373.25758.17772156949194131786.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: c30be431c90a4023be39e13cb721ae81df9d4573 Gitweb: https://git.kernel.org/tip/c30be431c90a4023be39e13cb721ae81df9d4573 Author: Zhang Qiao AuthorDate: Wed, 15 Sep 2021 14:40:30 +08:00 Committer: Peter Zijlstra CommitterDate: Thu, 07 Oct 2021 13:51:17 +02:00 kernel/sched: Fix sched_fork() access an invalid sched_task_group There is a small race between copy_process() and sched_fork() where child->sched_task_group point to an already freed pointer. parent doing fork() | someone moving the parent | to another cgroup -------------------------------+------------------------------- copy_process() + dup_task_struct()<1> parent move to another cgroup, and free the old cgroup. <2> + sched_fork() + __set_task_cpu()<3> + task_fork_fair() + sched_slice()<4> In the worst case, this bug can lead to "use-after-free" and cause panic as shown above: (1) parent copy its sched_task_group to child at <1>; (2) someone move the parent to another cgroup and free the old cgroup at <2>; (3) the sched_task_group and cfs_rq that belong to the old cgroup will be accessed at <3> and <4>, which cause a panic: [] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 [] PGD 8000001fa0a86067 P4D 8000001fa0a86067 PUD 2029955067 PMD 0 [] Oops: 0000 [#1] SMP PTI [] CPU: 7 PID: 648398 Comm: ebizzy Kdump: loaded Tainted: G OE --------- - - 4.18.0.x86_64+ #1 [] RIP: 0010:sched_slice+0x84/0xc0 [] Call Trace: [] task_fork_fair+0x81/0x120 [] sched_fork+0x132/0x240 [] copy_process.part.5+0x675/0x20e0 [] ? __handle_mm_fault+0x63f/0x690 [] _do_fork+0xcd/0x3b0 [] do_syscall_64+0x5d/0x1d0 [] entry_SYSCALL_64_after_hwframe+0x65/0xca [] RIP: 0033:0x7f04418cd7e1 Between cgroup_can_fork() and cgroup_post_fork(), the cgroup membership and thus sched_task_group can't change. So update child's sched_task_group at sched_post_fork() and move task_fork() and __set_task_cpu() (where accees the sched_task_group) from sched_fork() to sched_post_fork(). Fixes: 8323f26ce342 ("sched: Fix race in task_group") Signed-off-by: Zhang Qiao Signed-off-by: Peter Zijlstra (Intel) Acked-by: Tejun Heo Link: https://lkml.kernel.org/r/20210915064030.2231-1-zhangqiao22@huawei.com --- include/linux/sched/task.h | 3 ++- kernel/fork.c | 2 +- kernel/sched/core.c | 43 ++++++++++++++++++------------------- 3 files changed, 25 insertions(+), 23 deletions(-) diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index ef02be8..ba88a69 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -54,7 +54,8 @@ extern asmlinkage void schedule_tail(struct task_struct *prev); extern void init_idle(struct task_struct *idle, int cpu); extern int sched_fork(unsigned long clone_flags, struct task_struct *p); -extern void sched_post_fork(struct task_struct *p); +extern void sched_post_fork(struct task_struct *p, + struct kernel_clone_args *kargs); extern void sched_dead(struct task_struct *p); void __noreturn do_task_dead(void); diff --git a/kernel/fork.c b/kernel/fork.c index 38681ad..0e4251d 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2405,7 +2405,7 @@ static __latent_entropy struct task_struct *copy_process( write_unlock_irq(&tasklist_lock); proc_fork_connector(p); - sched_post_fork(p); + sched_post_fork(p, args); cgroup_post_fork(p, args); perf_event_fork(p); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3b55ef9..935c2da 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4343,8 +4343,6 @@ int sysctl_schedstats(struct ctl_table *table, int write, void *buffer, */ int sched_fork(unsigned long clone_flags, struct task_struct *p) { - unsigned long flags; - __sched_fork(clone_flags, p); /* * We mark the process as NEW here. This guarantees that @@ -4390,24 +4388,6 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) init_entity_runnable_average(&p->se); - /* - * The child is not yet in the pid-hash so no cgroup attach races, - * and the cgroup is pinned to this child due to cgroup_fork() - * is ran before sched_fork(). - * - * Silence PROVE_RCU. - */ - raw_spin_lock_irqsave(&p->pi_lock, flags); - rseq_migrate(p); - /* - * We're setting the CPU for the first time, we don't migrate, - * so use __set_task_cpu(). - */ - __set_task_cpu(p, smp_processor_id()); - if (p->sched_class->task_fork) - p->sched_class->task_fork(p); - raw_spin_unlock_irqrestore(&p->pi_lock, flags); - #ifdef CONFIG_SCHED_INFO if (likely(sched_info_on())) memset(&p->sched_info, 0, sizeof(p->sched_info)); @@ -4423,8 +4403,29 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) return 0; } -void sched_post_fork(struct task_struct *p) +void sched_post_fork(struct task_struct *p, struct kernel_clone_args *kargs) { + unsigned long flags; +#ifdef CONFIG_CGROUP_SCHED + struct task_group *tg; +#endif + + raw_spin_lock_irqsave(&p->pi_lock, flags); +#ifdef CONFIG_CGROUP_SCHED + tg = container_of(kargs->cset->subsys[cpu_cgrp_id], + struct task_group, css); + p->sched_task_group = autogroup_task_group(p, tg); +#endif + rseq_migrate(p); + /* + * We're setting the CPU for the first time, we don't migrate, + * so use __set_task_cpu(). + */ + __set_task_cpu(p, smp_processor_id()); + if (p->sched_class->task_fork) + p->sched_class->task_fork(p); + raw_spin_unlock_irqrestore(&p->pi_lock, flags); + uclamp_post_fork(p); }