[PATCH] update mq_notify to use a struct pid

Message queues can signal a process waiting for a message.

This patch replaces the pid_t value with a struct pid to avoid pid wrap
around problems.

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Acked-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

ipc/mqueue.c

@@ -73,7 +73,7 @@ struct mqueue_inode_info {
 	struct mq_attr attr;
 
 	struct sigevent notify;
-	pid_t notify_owner;
+	struct pid* notify_owner;
 	struct user_struct *user;	/* user who created, for accounting */
 	struct sock *notify_sock;
 	struct sk_buff *notify_cookie;
@@ -134,7 +134,7 @@ static struct inode *mqueue_get_inode(struct super_block *sb, int mode,
 			INIT_LIST_HEAD(&info->e_wait_q[0].list);
 			INIT_LIST_HEAD(&info->e_wait_q[1].list);
 			info->messages = NULL;
-			info->notify_owner = 0;
+			info->notify_owner = NULL;
 			info->qsize = 0;
 			info->user = NULL;	/* set when all is ok */
 			memset(&info->attr, 0, sizeof(info->attr));
@@ -338,7 +338,7 @@ static ssize_t mqueue_read_file(struct file *filp, char __user *u_data,
 			(info->notify_owner &&
 			 info->notify.sigev_notify == SIGEV_SIGNAL) ?
 				info->notify.sigev_signo : 0,
-			info->notify_owner);
+			pid_nr(info->notify_owner));
 	spin_unlock(&info->lock);
 	buffer[sizeof(buffer)-1] = '\0';
 	slen = strlen(buffer)+1;
@@ -363,7 +363,7 @@ static int mqueue_flush_file(struct file *filp, fl_owner_t id)
 	struct mqueue_inode_info *info = MQUEUE_I(filp->f_dentry->d_inode);
 
 	spin_lock(&info->lock);
-	if (current->tgid == info->notify_owner)
+	if (task_tgid(current) == info->notify_owner)
 		remove_notification(info);
 
 	spin_unlock(&info->lock);
@@ -518,8 +518,8 @@ static void __do_notify(struct mqueue_inode_info *info)
 			sig_i.si_pid = current->tgid;
 			sig_i.si_uid = current->uid;
 
-			kill_proc_info(info->notify.sigev_signo,
-				       &sig_i, info->notify_owner);
+			kill_pid_info(info->notify.sigev_signo,
+				      &sig_i, info->notify_owner);
 			break;
 		case SIGEV_THREAD:
 			set_cookie(info->notify_cookie, NOTIFY_WOKENUP);
@@ -528,7 +528,8 @@ static void __do_notify(struct mqueue_inode_info *info)
 			break;
 		}
 		/* after notification unregisters process */
-		info->notify_owner = 0;
+		put_pid(info->notify_owner);
+		info->notify_owner = NULL;
 	}
 	wake_up(&info->wait_q);
 }
@@ -566,12 +567,13 @@ static long prepare_timeout(const struct timespec __user *u_arg)
 
 static void remove_notification(struct mqueue_inode_info *info)
 {
-	if (info->notify_owner != 0 &&
+	if (info->notify_owner != NULL &&
 	    info->notify.sigev_notify == SIGEV_THREAD) {
 		set_cookie(info->notify_cookie, NOTIFY_REMOVED);
 		netlink_sendskb(info->notify_sock, info->notify_cookie, 0);
 	}
-	info->notify_owner = 0;
+	put_pid(info->notify_owner);
+	info->notify_owner = NULL;
 }
 
 static int mq_attr_ok(struct mq_attr *attr)
@@ -1062,11 +1064,11 @@ retry:
 	ret = 0;
 	spin_lock(&info->lock);
 	if (u_notification == NULL) {
-		if (info->notify_owner == current->tgid) {
+		if (info->notify_owner == task_tgid(current)) {
 			remove_notification(info);
 			inode->i_atime = inode->i_ctime = CURRENT_TIME;
 		}
-	} else if (info->notify_owner != 0) {
+	} else if (info->notify_owner != NULL) {
 		ret = -EBUSY;
 	} else {
 		switch (notification.sigev_notify) {
@@ -1086,7 +1088,8 @@ retry:
 			info->notify.sigev_notify = SIGEV_SIGNAL;
 			break;
 		}
-		info->notify_owner = current->tgid;
+
+		info->notify_owner = get_pid(task_tgid(current));
 		inode->i_atime = inode->i_ctime = CURRENT_TIME;
 	}
 	spin_unlock(&info->lock);