coda: Restrict coda messages to the initial user namespace

Remove the slight chance that uids and gids in coda messages will be
interpreted in the wrong user namespace.

- Only allow processes in the initial user namespace to open the coda
  character device to communicate with coda filesystems.
- Explicitly convert the uids in the coda header into the initial user
  namespace.
- In coda_vattr_to_attr make kuids and kgids from the initial user
  namespace uids and gids in struct coda_vattr that just came from
  userspace.
- In coda_iattr_to_vattr convert kuids and kgids into uids and gids
  in the intial user namespace and store them in struct coda_vattr for
  sending to coda userspace programs.

Nothing needs to be changed with mounts as coda does not support
being mounted in anything other than the initial user namespace.

Cc: Jan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/coda/coda_linux.c b/fs/coda/coda_linux.c
index 854ace712685..2849f41e72a2 100644
--- a/fs/coda/coda_linux.c
+++ b/fs/coda/coda_linux.c
@@ -100,9 +100,9 @@ void coda_vattr_to_iattr(struct inode *inode, struct coda_vattr *attr)
         if (attr->va_mode != (u_short) -1)
                 inode->i_mode = attr->va_mode | inode_type;
         if (attr->va_uid != -1) 
-                inode->i_uid = (uid_t) attr->va_uid;
+                inode->i_uid = make_kuid(&init_user_ns, (uid_t) attr->va_uid);
         if (attr->va_gid != -1)
-                inode->i_gid = (gid_t) attr->va_gid;
+                inode->i_gid = make_kgid(&init_user_ns, (gid_t) attr->va_gid);
         if (attr->va_nlink != -1)
                 set_nlink(inode, attr->va_nlink);
         if (attr->va_size != -1)
@@ -171,10 +171,10 @@ void coda_iattr_to_vattr(struct iattr *iattr, struct coda_vattr *vattr)
                 vattr->va_mode = iattr->ia_mode;
         }
         if ( valid & ATTR_UID ) {
-                vattr->va_uid = (vuid_t) iattr->ia_uid;
+                vattr->va_uid = (vuid_t) from_kuid(&init_user_ns, iattr->ia_uid);
         }
         if ( valid & ATTR_GID ) {
-                vattr->va_gid = (vgid_t) iattr->ia_gid;
+                vattr->va_gid = (vgid_t) from_kgid(&init_user_ns, iattr->ia_gid);
         }
         if ( valid & ATTR_SIZE ) {
                 vattr->va_size = iattr->ia_size;