| Date | Mon, 10 Nov 2014 23:00:26 +0100 | From | Oleg Nesterov <> | Subject | [PATCH 1/5] sched_show_task: fix unsafe usage of ->real_parent |
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rcu_read_lock() can not protect p->real_parent if release_task(p) was already called, change sched_show_task() to check pis_alive() like other users do.
Note: we need some helpers to cleanup the code like this. And it seems that that the usage of cpu_curr(cpu) in dump_cpu_task() is not safe too.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/sched/core.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 240157c..1ec75c9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4572,8 +4572,10 @@ void sched_show_task(struct task_struct *p) #ifdef CONFIG_DEBUG_STACK_USAGE free = stack_not_used(p); #endif + ppid = 0; rcu_read_lock(); - ppid = task_pid_nr(rcu_dereference(p->real_parent)); + if (pid_alive(p)) + ppid = task_pid_nr(rcu_dereference(p->real_parent)); rcu_read_unlock(); printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free, task_pid_nr(p), ppid, -- 1.5.5.1
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