From 3a515e4a62dbf7e4c213740268a5267faa69e5b2 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 8 Feb 2008 04:19:07 -0800 Subject: [PATCH] wait_task_continued/zombie: don't use task_pid_nr_ns() lockless Surprise, the other two wait_task_*() functions also abuse the task_pid_nr_ns() function, and may cause read-after-free or report nr == 0 in wait_task_continued(). wait_task_zombie() doesn't have this problem, but it is still better to cache pid_t rather than call task_pid_nr_ns() three times on the saved pid_namespace. Signed-off-by: Oleg Nesterov Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/exit.c | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index ee607720ae58..dee8b4d63403 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1189,12 +1189,9 @@ static int wait_task_zombie(struct task_struct *p, int noreap, { unsigned long state; int retval, status, traced; - struct pid_namespace *ns; - - ns = current->nsproxy->pid_ns; + pid_t pid = task_pid_nr_ns(p, current->nsproxy->pid_ns); if (unlikely(noreap)) { - pid_t pid = task_pid_nr_ns(p, ns); uid_t uid = p->uid; int exit_code = p->exit_code; int why, status; @@ -1313,11 +1310,11 @@ static int wait_task_zombie(struct task_struct *p, int noreap, retval = put_user(status, &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; if (traced) { write_lock_irq(&tasklist_lock); @@ -1436,7 +1433,6 @@ static int wait_task_continued(struct task_struct *p, int noreap, int retval; pid_t pid; uid_t uid; - struct pid_namespace *ns; if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) return 0; @@ -1451,8 +1447,7 @@ static int wait_task_continued(struct task_struct *p, int noreap, p->signal->flags &= ~SIGNAL_STOP_CONTINUED; spin_unlock_irq(&p->sighand->siglock); - ns = current->nsproxy->pid_ns; - pid = task_pid_nr_ns(p, ns); + pid = task_pid_nr_ns(p, current->nsproxy->pid_ns); uid = p->uid; get_task_struct(p); read_unlock(&tasklist_lock); @@ -1463,7 +1458,7 @@ static int wait_task_continued(struct task_struct *p, int noreap, if (!retval && stat_addr) retval = put_user(0xffff, stat_addr); if (!retval) - retval = task_pid_nr_ns(p, ns); + retval = pid; } else { retval = wait_noreap_copyout(p, pid, uid, CLD_CONTINUED, SIGCONT, -- 2.20.1