From: shikemeng <shikemeng@huawei.com>
To: <mingo@redhat.com>, <peterz@infradead.org>
Cc: <linux-kernel@vger.kernel.org>
Subject: [PATCH] sched: fix migration to invalid cpu in __set_cpus_allowed_ptr
Date: Sun, 15 Sep 2019 03:07:47 +0000 [thread overview]
Message-ID: <1568516867-11300-1-git-send-email-shikemeng@huawei.com> (raw)
From: <shikemeng@huawei.com>
reason: migration to invalid cpu in __set_cpus_allowed_ptr
archive path: patches/euleros/sched
Oops occur when running qemu on arm64:
Unable to handle kernel paging request at virtual address ffff000008effe40
Internal error: Oops: 96000007 [#1] SMP
Process migration/0 (pid: 12, stack limit = 0x00000000084e3736)
pstate: 20000085 (nzCv daIf -PAN -UAO)
pc : __ll_sc___cmpxchg_case_acq_4+0x4/0x20
lr : move_queued_task.isra.21+0x124/0x298
...
Call trace:
__ll_sc___cmpxchg_case_acq_4+0x4/0x20
__migrate_task+0xc8/0xe0
migration_cpu_stop+0x170/0x180
cpu_stopper_thread+0xec/0x178
smpboot_thread_fn+0x1ac/0x1e8
kthread+0x134/0x138
ret_from_fork+0x10/0x18
__set_cpus_allowed_ptr will choose an active dest_cpu in affinity mask to migrage the process if process is not
currently running on any one of the CPUs specified in affinity mask.__set_cpus_allowed_ptr will choose an invalid
dest_cpu(>= nr_cpu_ids, 1024 in my virtual machine) if CPUS in affinity mask are deactived by cpu_down after
cpumask_intersects check.Cpumask_test_cpu of dest_cpu afterwards is overflow and may passes if corresponding bit
is coincidentally set.As a consequence, kernel will access a invalid rq address associate with the invalid cpu in
migration_cpu_stop->__migrate_task->move_queued_task and the Oops occurs. Process as follows may trigger the Oops:
1) A process repeatedly bind itself to cpu0 and cpu1 in turn by calling sched_setaffinity
2) A shell script repeatedly "echo 0 > /sys/devices/system/cpu/cpu1/online" and "echo 1 > /sys/devices/system/cpu/cpu1/online" in turn
3) Oops appears if the invalid cpu is set in memory after tested cpumask.
Change-Id: I9c2f95aecd3da568991b7408397215f26c990e40
Signed-off-by: <shikemeng@huawei.com>
---
kernel/sched/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4b63fef..5181ea9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1112,7 +1112,8 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
if (cpumask_equal(&p->cpus_allowed, new_mask))
goto out;
- if (!cpumask_intersects(new_mask, cpu_valid_mask)) {
+ dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask);
+ if (dest_cpu >= nr_cpu_ids) {
ret = -EINVAL;
goto out;
}
@@ -1133,7 +1134,6 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
if (cpumask_test_cpu(task_cpu(p), new_mask))
goto out;
- dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask);
if (task_running(rq, p) || p->state == TASK_WAKING) {
struct migration_arg arg = { p, dest_cpu };
/* Need help from migration thread: drop lock and wait. */
--
1.8.3.1
next reply other threads:[~2019-09-15 3:25 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-15 3:07 shikemeng [this message]
2019-09-15 17:00 ` [PATCH] sched: fix migration to invalid cpu in __set_cpus_allowed_ptr Valentin Schneider
-- strict thread matches above, loose matches on Subject: below --
2019-09-12 1:55 shikemeng
2019-09-12 22:09 ` Valentin Schneider
2019-09-15 8:21 ` Re: " shikemeng
2019-09-15 14:33 ` Valentin Schneider
2019-09-23 15:43 ` Dietmar Eggemann
2019-09-23 16:06 ` Valentin Schneider
2019-09-24 14:09 ` Dietmar Eggemann
2019-09-24 16:12 ` Valentin Schneider
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