[PATCH] introduce get_task_pid() to fix unsafe get_pid()

proc_pid_make_inode:

	ei->pid = get_pid(task_pid(task));

I think this is not safe.  get_pid() can be preempted after checking "pid
!= NULL".  Then the task exits, does detach_pid(), and RCU frees the pid.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/pid.h b/include/linux/pid.h
index 7e39767b4c60..17b9e04d3586 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -68,6 +68,8 @@ extern struct task_struct *FASTCALL(pid_task(struct pid *pid, enum pid_type));
 extern struct task_struct *FASTCALL(get_pid_task(struct pid *pid,
                                                 enum pid_type));
 
+extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type);
+
 /*
  * attach_pid() and detach_pid() must be called with the tasklist_lock
  * write-held.