summaryrefslogtreecommitdiff
path: root/kernel
diff options
context:
space:
mode:
authorPeter Zijlstra <peterz@infradead.org>2022-02-14 12:16:57 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-03-08 21:12:49 +0300
commit3411613611a5cddf7e80908010dc87cb527dd13b (patch)
treea902744348d527aa95f37bbeb327c561efcc11f7 /kernel
parent3d76a995f6469379c48be9494c66bcfca973bca1 (diff)
downloadlinux-3411613611a5cddf7e80908010dc87cb527dd13b.tar.xz
sched: Fix yet more sched_fork() races
commit b1e8206582f9d680cff7d04828708c8b6ab32957 upstream. 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 <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Tadeusz Struk <tadeusz.struk@linaro.org> Tested-by: Zhang Qiao <zhangqiao22@huawei.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lkml.kernel.org/r/YgoeCbwj5mbCR0qA@hirez.programming.kicks-ass.net Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/fork.c13
-rw-r--r--kernel/sched/core.c34
2 files changed, 33 insertions, 14 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 28aee1a8875b..89475c994ca9 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2297,6 +2297,17 @@ static __latent_entropy struct task_struct *copy_process(
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
* not want user-space to be able to predict the process start-time by
@@ -2405,7 +2416,7 @@ static __latent_entropy struct task_struct *copy_process(
fd_install(pidfd, pidfile);
proc_fork_connector(p);
- sched_post_fork(p, args);
+ sched_post_fork(p);
cgroup_post_fork(p, args);
perf_event_fork(p);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 57e5c7914296..a0747eaa2dba 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1199,9 +1199,8 @@ 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;
@@ -4359,7 +4358,7 @@ 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
@@ -4377,6 +4376,7 @@ 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));
@@ -4392,18 +4392,23 @@ 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);
/*
@@ -4414,7 +4419,10 @@ 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);
}
@@ -6903,7 +6911,7 @@ 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);
@@ -7194,7 +7202,7 @@ 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);
}
/*
@@ -9432,7 +9440,7 @@ 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: