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authorOleg Nesterov <oleg@redhat.com>2013-07-03 15:08:31 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-03 16:08:03 -0700
commit8190773985141f063e1d6dc10200527c655abfb5 (patch)
tree5c148834f047748dfa2ce3500236b89656976567
parent80628ca06c5d42929de6bc22c0a41589a834d151 (diff)
downloadop-kernel-dev-8190773985141f063e1d6dc10200527c655abfb5.zip
op-kernel-dev-8190773985141f063e1d6dc10200527c655abfb5.tar.gz
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>
-rw-r--r--include/linux/pid.h6
-rw-r--r--kernel/fork.c16
-rw-r--r--kernel/pid.c12
3 files changed, 19 insertions, 15 deletions
diff --git a/include/linux/pid.h b/include/linux/pid.h
index a089a3c..23705a5 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -86,11 +86,9 @@ extern struct task_struct *get_pid_task(struct pid *pid, enum pid_type);
extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type);
/*
- * attach_pid() and detach_pid() must be called with the tasklist_lock
- * write-held.
+ * these helpers must be called with the tasklist_lock write-held.
*/
-extern void attach_pid(struct task_struct *task, enum pid_type type,
- struct pid *pid);
+extern void attach_pid(struct task_struct *task, enum pid_type);
extern void detach_pid(struct task_struct *task, enum pid_type);
extern void change_pid(struct task_struct *task, enum pid_type,
struct pid *pid);
diff --git a/kernel/fork.c b/kernel/fork.c
index 417cb86..7d6962f 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++;
}
diff --git a/kernel/pid.c b/kernel/pid.c
index 0db3e79..61980cef 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -373,14 +373,10 @@ EXPORT_SYMBOL_GPL(find_vpid);
/*
* attach_pid() must be called with the tasklist_lock write-held.
*/
-void attach_pid(struct task_struct *task, enum pid_type type,
- struct pid *pid)
+void attach_pid(struct task_struct *task, enum pid_type type)
{
- struct pid_link *link;
-
- link = &task->pids[type];
- link->pid = pid;
- hlist_add_head_rcu(&link->node, &pid->tasks[type]);
+ struct pid_link *link = &task->pids[type];
+ hlist_add_head_rcu(&link->node, &link->pid->tasks[type]);
}
static void __change_pid(struct task_struct *task, enum pid_type type,
@@ -412,7 +408,7 @@ void change_pid(struct task_struct *task, enum pid_type type,
struct pid *pid)
{
__change_pid(task, type, pid);
- attach_pid(task, type, pid);
+ attach_pid(task, type);
}
/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
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