FAILED: patch "[PATCH] sched: Fix yet more sched_fork() races" failed to apply to 5.15-stable tree
Subsystems (4)
[email protected]
maintainerThe patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From b1e8206582f9d680cff7d04828708c8b6ab32957 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <[email protected]>
Date: Mon, 14 Feb 2022 10:16:57 +0100
Subject: [PATCH] sched: Fix yet more sched_fork() races
Where commit 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group") fixed a fork race vs cgroup, it opened up a race vs syscalls by not placing the task on the runqueue before it gets exposed through the pidhash.
Commit 13765de8148f ("sched/fair: Fix fault in reweight_entity") is trying to fix a single instance of this, instead fix the whole class of issues, effectively reverting this commit.
Fixes 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group")
Reported-by Linus Torvalds <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Tested-by Tadeusz Struk <[email protected]>
Tested-by Zhang Qiao <[email protected]>
Tested-by Dietmar Eggemann <[email protected]>
include/linux/sched/task.h +2 -2
@@ -54,8 +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, -struct kernel_clone_args *kargs); +extern void sched_cgroup_fork (struct task_struct *p,struct kernel_clone_args *kargs); +extern void sched_post_fork (struct task_struct *p);extern void sched_dead (struct task_struct *p);void __noreturn do_task_dead (void );
kernel/fork.c +12 -1
@@ -2266,6 +2266,17 @@ static __latent_entropy struct task_struct *copy_process(if (retval) goto bad_fork_put_pidfd; +/* +* Now that the cgroups are pinned, re-clone the parent cgroup and put +* the new task on the correct runqueue. All this *before* the task +* becomes visible. +* +* This isn't part of ->can_fork() because while the re-cloning is +* cgroup specific, it unconditionally needs to place the task on a +* runqueue. +*/ +sched_cgroup_fork (p, args); +/* * From this point on we must avoid any synchronous user-space * communication until we take the tasklist-lock. In particular, we do
@@ -2376,7 +2387,7 @@ static __latent_entropy struct task_struct *copy_process(write_unlock_irq (&tasklist_lock);proc_fork_connector (p); -sched_post_fork (p, args); +sched_post_fork (p);cgroup_post_fork (p, args);perf_event_fork (p);
kernel/sched/core.c +21 -13
@@ -1214,9 +1214,8 @@ int tg_nop(struct task_group *tg, void *data) }#endif -static void set_load_weight (struct task_struct *p) +static void set_load_weight (struct task_struct *p,bool update_load) { -bool update_load = !(READ_ONCE (p->__state) &TASK_NEW );int prio = p->static_prio -MAX_RT_PRIO ;struct load_weight *load = &p->se.load;
@@ -4407,7 +4406,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) p->static_prio =NICE_TO_PRIO (0 ); p->prio = p->normal_prio = p->static_prio; -set_load_weight (p); +set_load_weight (p, false);/* * We don't need the reset flag anymore after the fork. It has
@@ -4425,6 +4424,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)init_entity_runnable_average (&p->se); +#ifdef CONFIG_SCHED_INFO if (likely (sched_info_on ()))memset (&p->sched_info,0 ,sizeof (p->sched_info));
@@ -4440,18 +4440,23 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)return 0 ; } -void sched_post_fork (struct task_struct *p,struct kernel_clone_args *kargs) +void sched_cgroup_fork (struct task_struct *p,struct kernel_clone_args *kargs) {unsigned long flags; -#ifdef CONFIG_CGROUP_SCHED -struct task_group *tg; -#endif +/* +* Because we're not yet on the pid-hash, p->pi_lock isn't strictly +* required yet, but lockdep gets upset if rules are violated. +*/ 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); +if (1 ) { +struct task_group *tg; + tg =container_of (kargs->cset->subsys[cpu_cgrp_id], + struct task_group, css); + tg =autogroup_task_group (p, tg); + p->sched_task_group = tg; + }#endif rseq_migrate (p);/*
@@ -4462,7 +4467,10 @@ void sched_post_fork(struct task_struct *p, struct kernel_clone_args *kargs)if (p->sched_class->task_fork) p->sched_class->task_fork (p);raw_spin_unlock_irqrestore (&p->pi_lock, flags); +} +void sched_post_fork (struct task_struct *p) +{uclamp_post_fork (p); }
@@ -6922,7 +6930,7 @@ void set_user_nice(struct task_struct *p, long nice)put_prev_task (rq, p); p->static_prio =NICE_TO_PRIO (nice); -set_load_weight (p); +set_load_weight (p, true); old_prio = p->prio; p->prio =effective_prio (p);
@@ -7213,7 +7221,7 @@ static void __setscheduler_params(struct task_struct *p,*/ p->rt_priority = attr->sched_priority; p->normal_prio =normal_prio (p); -set_load_weight (p); +set_load_weight (p, true); }/*
@@ -9446,7 +9454,7 @@ void __init sched_init(void)#endif } -set_load_weight (&init_task); +set_load_weight (&init_task, false);/* * The boot idle thread does lazy MMU switching as well: