pid namespaces: introduce MS_KERNMOUNT flag
This flag tells the .get_sb callback that this is a kern_mount() call so that
it can trust *data pointer to be valid in-kernel one. If this flag is passed
from the user process, it is cleared since the *data pointer is not a valid
kernel object.
Running a few steps forward - this will be needed for proc to create the
superblock and store a valid pid namespace on it during the namespace
creation. The reason, why the namespace cannot live without proc mount is
described in the appropriate patch.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/namespace.c b/fs/namespace.c
index 07daa79..8607529 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1411,7 +1411,7 @@
mnt_flags |= MNT_RELATIME;
flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
- MS_NOATIME | MS_NODIRATIME | MS_RELATIME);
+ MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT);
/* ... and get the mountpoint */
retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
diff --git a/fs/super.c b/fs/super.c
index feaae7e..d28fde7 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -944,9 +944,9 @@
return mnt;
}
-struct vfsmount *kern_mount(struct file_system_type *type)
+struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
{
- return vfs_kern_mount(type, 0, type->name, NULL);
+ return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
}
-EXPORT_SYMBOL(kern_mount);
+EXPORT_SYMBOL_GPL(kern_mount_data);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3efff12..1657e99 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -123,6 +123,7 @@
#define MS_SLAVE (1<<19) /* change to slave */
#define MS_SHARED (1<<20) /* change to shared */
#define MS_RELATIME (1<<21) /* Update atime relative to mtime/ctime. */
+#define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */
#define MS_ACTIVE (1<<30)
#define MS_NOUSER (1<<31)
@@ -1459,7 +1460,8 @@
extern int register_filesystem(struct file_system_type *);
extern int unregister_filesystem(struct file_system_type *);
-extern struct vfsmount *kern_mount(struct file_system_type *);
+extern struct vfsmount *kern_mount_data(struct file_system_type *, void *data);
+#define kern_mount(type) kern_mount_data(type, NULL)
extern int may_umount_tree(struct vfsmount *);
extern int may_umount(struct vfsmount *);
extern void umount_tree(struct vfsmount *, int, struct list_head *);