Commit 2ae448ef authored Apr 02, 2009 by Oleg Nesterov Committed by Linus Torvalds Apr 02, 2009

pids: improve get_task_pid() to fix the unsafe sys_wait4()->task_pgrp()

sys_wait4() does get_pid(task_pgrp(current)), this is not safe.  We can
add rcu lock/unlock around, but we already have get_task_pid() which can
be improved to handle the special pids in more reliable manner.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 6dda81f4

kernel/exit.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1737,7 +1737,7 @@ SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
		pid = find_get_pid(-upid);
		} else if (upid == 0) {
		type = PIDTYPE_PGID;
		pid = get_pid(task_pgrp(current));
		pid = get_task_pid(current, PIDTYPE_PGID);
		} else /* upid > 0 */ {
		type = PIDTYPE_PID;
		pid = find_get_pid(upid);

kernel/pid.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -403,6 +403,8 @@ struct pid get_task_pid(struct task_struct task, enum pid_type type)
		{
		struct pid *pid;
		rcu_read_lock();
		if (type != PIDTYPE_PID)
		task = task->group_leader;
		pid = get_pid(task->pids[type].pid);
		rcu_read_unlock();
		return pid;