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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>
This commit is contained in:
Oleg Nesterov 2009-04-02 16:58:36 -07:00 committed by Linus Torvalds
parent 6dda81f438
commit 2ae448efc8
2 changed files with 3 additions and 1 deletions
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2
kernel/exit.c
View File

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

2
kernel/pid.c
View File

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