Commit c170b793 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Greg Kroah-Hartman

pids: make task_tgid_nr_ns() safe

commit dd1c1f2f upstream.

This was reported many times, and this was even mentioned in commit
52ee2dfd ("pids: refactor vnr/nr_ns helpers to make them safe") but
somehow nobody bothered to fix the obvious problem: task_tgid_nr_ns() is
not safe because task->group_leader points to nowhere after the exiting
task passes exit_notify(), rcu_read_lock() can not help.

We really need to change __unhash_process() to nullify group_leader,
parent, and real_parent, but this needs some cleanups.  Until then we
can turn task_tgid_nr_ns() into another user of __task_pid_nr_ns() and
fix the problem.
Reported-by: default avatarTroy Kensinger <tkensinger@google.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e950adf8
......@@ -8,7 +8,9 @@ enum pid_type
PIDTYPE_PID,
PIDTYPE_PGID,
PIDTYPE_SID,
PIDTYPE_MAX
PIDTYPE_MAX,
/* only valid to __task_pid_nr_ns() */
__PIDTYPE_TGID
};
/*
......
......@@ -1132,13 +1132,6 @@ static inline pid_t task_tgid_nr(struct task_struct *tsk)
return tsk->tgid;
}
extern pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns);
static inline pid_t task_tgid_vnr(struct task_struct *tsk)
{
return pid_vnr(task_tgid(tsk));
}
/**
* pid_alive - check that a task structure is not stale
* @p: Task structure to be checked.
......@@ -1154,23 +1147,6 @@ static inline int pid_alive(const struct task_struct *p)
return p->pids[PIDTYPE_PID].pid != NULL;
}
static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns)
{
pid_t pid = 0;
rcu_read_lock();
if (pid_alive(tsk))
pid = task_tgid_nr_ns(rcu_dereference(tsk->real_parent), ns);
rcu_read_unlock();
return pid;
}
static inline pid_t task_ppid_nr(const struct task_struct *tsk)
{
return task_ppid_nr_ns(tsk, &init_pid_ns);
}
static inline pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
{
return __task_pid_nr_ns(tsk, PIDTYPE_PGID, ns);
......@@ -1192,6 +1168,33 @@ static inline pid_t task_session_vnr(struct task_struct *tsk)
return __task_pid_nr_ns(tsk, PIDTYPE_SID, NULL);
}
static inline pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
{
return __task_pid_nr_ns(tsk, __PIDTYPE_TGID, ns);
}
static inline pid_t task_tgid_vnr(struct task_struct *tsk)
{
return __task_pid_nr_ns(tsk, __PIDTYPE_TGID, NULL);
}
static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns)
{
pid_t pid = 0;
rcu_read_lock();
if (pid_alive(tsk))
pid = task_tgid_nr_ns(rcu_dereference(tsk->real_parent), ns);
rcu_read_unlock();
return pid;
}
static inline pid_t task_ppid_nr(const struct task_struct *tsk)
{
return task_ppid_nr_ns(tsk, &init_pid_ns);
}
/* Obsolete, do not use: */
static inline pid_t task_pgrp_nr(struct task_struct *tsk)
{
......
......@@ -527,8 +527,11 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
if (!ns)
ns = task_active_pid_ns(current);
if (likely(pid_alive(task))) {
if (type != PIDTYPE_PID)
if (type != PIDTYPE_PID) {
if (type == __PIDTYPE_TGID)
type = PIDTYPE_PID;
task = task->group_leader;
}
nr = pid_nr_ns(rcu_dereference(task->pids[type].pid), ns);
}
rcu_read_unlock();
......@@ -537,12 +540,6 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
}
EXPORT_SYMBOL(__task_pid_nr_ns);
pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
{
return pid_nr_ns(task_tgid(tsk), ns);
}
EXPORT_SYMBOL(task_tgid_nr_ns);
struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
{
return ns_of_pid(task_pid(tsk));
......
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