[patch 04/10] add "permit user mounts" flag to namespaces

[Miklos Szeredi <miklos@szeredi.hu>]

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From: Miklos Szeredi <mszeredi@suse.cz>

If MNT_NS_PERMIT_USERMOUNTS flag is not set for the current namespace,
then unprivileged mounts will be denied.

By default this flag is cleared in all namespaces.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---

Index: linux/fs/namespace.c
===================================================================
--- linux.orig/fs/namespace.c	2007-04-12 16:50:16.000000000 +0200
+++ linux/fs/namespace.c	2007-04-12 16:50:17.000000000 +0200
@@ -1526,6 +1526,19 @@ dput_out:
 	return retval;
 }
 
+static struct mnt_namespace *alloc_ns(void)
+{
+	struct mnt_namespace *ns;
+
+	ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
+	if (ns) {
+		atomic_set(&ns->count, 1);
+		INIT_LIST_HEAD(&ns->list);
+		init_waitqueue_head(&ns->poll);
+	}
+	return ns;
+}
+
 /*
  * Allocate a new namespace structure and populate it with contents
  * copied from the namespace of the passed in task structure.
@@ -1537,15 +1550,10 @@ static struct mnt_namespace *dup_mnt_ns(
 	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
 	struct vfsmount *p, *q;
 
-	new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
+	new_ns = alloc_ns();
 	if (!new_ns)
 		return NULL;
 
-	atomic_set(&new_ns->count, 1);
-	INIT_LIST_HEAD(&new_ns->list);
-	init_waitqueue_head(&new_ns->poll);
-	new_ns->event = 0;
-
 	down_write(&namespace_sem);
 	/* First pass: copy the tree topology */
 	new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root,
@@ -1860,13 +1868,10 @@ static void __init init_mount_tree(void)
 	mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
 	if (IS_ERR(mnt))
 		panic("Can't create rootfs");
-	ns = kmalloc(sizeof(*ns), GFP_KERNEL);
+	ns = alloc_ns();
 	if (!ns)
 		panic("Can't allocate initial namespace");
-	atomic_set(&ns->count, 1);
-	INIT_LIST_HEAD(&ns->list);
-	init_waitqueue_head(&ns->poll);
-	ns->event = 0;
+
 	list_add(&mnt->mnt_list, &ns->list);
 	ns->root = mnt;
 	mnt->mnt_ns = ns;
Index: linux/include/linux/mnt_namespace.h
===================================================================
--- linux.orig/include/linux/mnt_namespace.h	2007-04-12 16:50:02.000000000 +0200
+++ linux/include/linux/mnt_namespace.h	2007-04-12 16:50:17.000000000 +0200
@@ -6,12 +6,16 @@
 #include <linux/sched.h>
 #include <linux/nsproxy.h>
 
+/* mnt_namespace flags */
+#define MNT_NS_PERMIT_USERMOUNTS	(1 << 0)
+
 struct mnt_namespace {
 	atomic_t		count;
 	struct vfsmount *	root;
 	struct list_head	list;
 	wait_queue_head_t poll;
 	int event;
+	int flags;
 };
 
 extern struct mnt_namespace *copy_mnt_ns(int, struct mnt_namespace *,

--