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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 <oleg@tv-sign.ru>
Looks-good-to: Roland McGrath <roland@redhat.com>
Acked-by: Pavel Emelyanov <xemul@openvz.org>
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 2007-11-28 16:21:24 -08:00 committed by Linus Torvalds
parent c2319540cd
commit c895078355
1 changed files with 4 additions and 5 deletions
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9
kernel/exit.c
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@ -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 @@ bail_ref:
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);