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| author | Oleg Nesterov <oleg@redhat.com> | 2013-07-03 15:08:31 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-07-03 16:08:03 -0700 |
| commit | 8190773985141f063e1d6dc10200527c655abfb5 (patch) | |
| tree | 5c148834f047748dfa2ce3500236b89656976567 /kernel/fork.c | |
| parent | 80628ca06c5d42929de6bc22c0a41589a834d151 (diff) | |
| download | linux-8190773985141f063e1d6dc10200527c655abfb5.tar.gz linux-8190773985141f063e1d6dc10200527c655abfb5.tar.bz2 linux-8190773985141f063e1d6dc10200527c655abfb5.zip | |
kernel/fork.c:copy_process(): don't add the uninitialized child to thread/task/pid lists
copy_process() adds the new child to thread_group/init_task.tasks list and
then does attach_pid(child, PIDTYPE_PID). This means that the lockless
next_thread() or next_task() can see this thread with the wrong pid. Say,
"ls /proc/pid/task" can list the same inode twice.
We could move attach_pid(child, PIDTYPE_PID) up, but in this case
find_task_by_vpid() can find the new thread before it was fully
initialized.
And this is already true for PIDTYPE_PGID/PIDTYPE_SID, With this patch
copy_process() initializes child->pids[*].pid first, then calls
attach_pid() to insert the task into the pid->tasks list.
attach_pid() no longer need the "struct pid*" argument, it is always
called after pid_link->pid was already set.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Sergey Dyasly <dserrg@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 417cb864e20c..7d6962fb6156 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1121,6 +1121,12 @@ static void posix_cpu_timers_init(struct task_struct *tsk) INIT_LIST_HEAD(&tsk->cpu_timers[2]); } +static inline void +init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) +{ + task->pids[type].pid = pid; +} + /* * This creates a new process as a copy of the old one, * but does not actually start it yet. @@ -1449,7 +1455,11 @@ static struct task_struct *copy_process(unsigned long clone_flags, if (likely(p->pid)) { ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); + init_task_pid(p, PIDTYPE_PID, pid); if (thread_group_leader(p)) { + init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); + init_task_pid(p, PIDTYPE_SID, task_session(current)); + if (is_child_reaper(pid)) { ns_of_pid(pid)->child_reaper = p; p->signal->flags |= SIGNAL_UNKILLABLE; @@ -1457,10 +1467,10 @@ static struct task_struct *copy_process(unsigned long clone_flags, p->signal->leader_pid = pid; p->signal->tty = tty_kref_get(current->signal->tty); - attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); - attach_pid(p, PIDTYPE_SID, task_session(current)); list_add_tail(&p->sibling, &p->real_parent->children); list_add_tail_rcu(&p->tasks, &init_task.tasks); + attach_pid(p, PIDTYPE_PGID); + attach_pid(p, PIDTYPE_SID); __this_cpu_inc(process_counts); } else { current->signal->nr_threads++; @@ -1470,7 +1480,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); } - attach_pid(p, PIDTYPE_PID, pid); + attach_pid(p, PIDTYPE_PID); nr_threads++; } |