From c895078355b6b6e05c60aa205892526dd3390f0a Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 28 Nov 2007 16:21:24 -0800 Subject: [PATCH] wait_task_stopped(): don't use task_pid_nr_ns() lockless wait_task_stopped(WNOWAIT) does task_pid_nr_ns() without tasklist/rcu lock, we can read an already freed memory. Use the cached pid_t value. Signed-off-by: Oleg Nesterov Looks-good-to: Roland McGrath Acked-by: Pavel Emelyanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/exit.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index cd0f1d4137a7..0a4a382ecf23 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1357,7 +1357,7 @@ static int wait_task_stopped(struct task_struct *p, int delayed_group_leader, int __user *stat_addr, struct rusage __user *ru) { int retval, exit_code; - struct pid_namespace *ns; + pid_t pid; if (!p->exit_code) return 0; @@ -1376,12 +1376,11 @@ static int wait_task_stopped(struct task_struct *p, int delayed_group_leader, * keep holding onto the tasklist_lock while we call getrusage and * possibly take page faults for user memory. */ - ns = current->nsproxy->pid_ns; + pid = task_pid_nr_ns(p, current->nsproxy->pid_ns); get_task_struct(p); read_unlock(&tasklist_lock); if (unlikely(noreap)) { - pid_t pid = task_pid_nr_ns(p, ns); uid_t uid = p->uid; int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED; @@ -1451,11 +1450,11 @@ static int wait_task_stopped(struct task_struct *p, int delayed_group_leader, if (!retval && infop) retval = put_user(exit_code, &infop->si_status); if (!retval && infop) - retval = put_user(task_pid_nr_ns(p, ns), &infop->si_pid); + retval = put_user(pid, &infop->si_pid); if (!retval && infop) retval = put_user(p->uid, &infop->si_uid); if (!retval) - retval = task_pid_nr_ns(p, ns); + retval = pid; put_task_struct(p); BUG_ON(!retval);