CRED: Pass credentials through dentry_open()

Pass credentials through dentry_open() so that the COW creds patch can have
SELinux's flush_unauthorized_files() pass the appropriate creds back to itself
when it opens its null chardev.

The security_dentry_open() call also now takes a creds pointer, as does the
dentry_open hook in struct security_operations.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 1151881..d9393f8 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -594,6 +594,7 @@
 static struct file *do_create(struct dentry *dir, struct dentry *dentry,
 			int oflag, mode_t mode, struct mq_attr __user *u_attr)
 {
+	const struct cred *cred = current_cred();
 	struct mq_attr attr;
 	struct file *result;
 	int ret;
@@ -618,7 +619,7 @@
 	if (ret)
 		goto out_drop_write;
 
-	result = dentry_open(dentry, mqueue_mnt, oflag);
+	result = dentry_open(dentry, mqueue_mnt, oflag, cred);
 	/*
 	 * dentry_open() took a persistent mnt_want_write(),
 	 * so we can now drop this one.
@@ -637,8 +638,10 @@
 /* Opens existing queue */
 static struct file *do_open(struct dentry *dentry, int oflag)
 {
-static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
-					MAY_READ | MAY_WRITE };
+	const struct cred *cred = current_cred();
+
+	static const int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
+						  MAY_READ | MAY_WRITE };
 
 	if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY)) {
 		dput(dentry);
@@ -652,7 +655,7 @@
 		return ERR_PTR(-EACCES);
 	}
 
-	return dentry_open(dentry, mqueue_mnt, oflag);
+	return dentry_open(dentry, mqueue_mnt, oflag, cred);
 }
 
 asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode,