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 <[email protected]> Cc: Louis Rilling <[email protected]> Cc: "Eric W. Biederman" <[email protected]> Cc: Pavel Emelyanov <[email protected]> Cc: Sukadev Bhattiprolu <[email protected]> Cc: Roland McGrath <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
yshchan · Apr 3, 2009 · 2ae448e · 2ae448e
1 parent 6dda81f
commit 2ae448e
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Showing 2 changed files with 3 additions and 1 deletion.
diff --git a/kernel/exit.c b/kernel/exit.c
@@ -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);

diff --git a/kernel/pid.c b/kernel/pid.c
@@ -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;