Fix si_pid value in mqueue do_notify()

From: Sukadev Bhattiprolu <[email protected]>
Date: Fri, 12 Dec 2008 17:50:08 -0800
Subject: [PATCH] Fix si_pid value in mqueue do_notify()

If a process registers for asynchronous notification on a POSIX message queue, it gets a signal and a siginfo_t structure when a message arrives on the message queue. The si_pid in the siginfo_t structure is set to the PID of the process that sent the message to the message queue.

The principle is the following:
. when mq_notify(SIGEV_SIGNAL) is called, the caller registers for
notification when a msg arrives. The associated pid structure is stroed into inode_info->notify_owner. Let's call this process P1.
. when mq_send() is called by say P2, P2 sends a signal to P1 to notify
him about msg arrival.

The way .si_pid is set today is not correct, since it doesn't take into account the fact that the process that is sending the message might not be in the same namespace as the notified one.

This patch proposes to set si_pid to the sender's pid into the notify_owner namespace.

Changelog[v2]:
- Moved ns_of_pid() to separate patch and simplified this patch.

---
 ipc/mqueue.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

index d9393f8..cf465ce 100644
@@ -506,7 +506,8 @@ static void __do_notify(struct mqueue_inode_info *info)
 			sig_i.si_errno = 0;
 			sig_i.si_code = SI_MESGQ;
 			sig_i.si_value = info->notify.sigev_value;
-			sig_i.si_pid = task_tgid_vnr(current);
+			sig_i.si_pid = task_tgid_nr_ns(current,
+						ns_of_pid(info->notify_owner));
 			sig_i.si_uid = current_uid();
 
 			kill_pid_info(info->notify.sigev_signo,

1.5.2.5