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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 <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2008-02-08 04:19:07 -08:00 committed by Linus Torvalds
parent f2cc3eb133
commit 3a515e4a62
1 changed files with 5 additions and 10 deletions
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15
kernel/exit.c
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@ -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,