[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, 2 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index a317eb2c4442..82da55b5cffe 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -958,7 +958,7 @@ static struct inode *proc_pid_make_inode(struct super_block * sb, struct task_st
         /*
          * grab the reference to task.
          */
-        ei->pid = get_pid(task_pid(task));
+        ei->pid = get_task_pid(task, PIDTYPE_PID);
         if (!ei->pid)
                 goto out_unlock;
 
@@ -1677,7 +1677,7 @@ static struct dentry *proc_base_instantiate(struct inode *dir,
         /*
          * grab the reference to the task.
          */
-        ei->pid = get_pid(task_pid(task));
+        ei->pid = get_task_pid(task, PIDTYPE_PID);
         if (!ei->pid)
                 goto out_iput;