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 <[e-mail]>
Signed-off-by: "Eric W. Biederman" <[e-mail]>

fs/coda/coda_linux.c

···
 	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)
···
                 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;

fs/coda/psdev.c

···
 	if (task_active_pid_ns(current) != &init_pid_ns)
 		return -EINVAL;
 
+	if (current_user_ns() != &init_user_ns)
+		return -EINVAL;
+
 	idx = iminor(inode);
 	if (idx < 0 || idx >= MAX_CODADEVS)
 		return -ENODEV;

fs/coda/upcall.c

···
         inp->ih.opcode = opcode;
 	inp->ih.pid = task_pid_nr_ns(current, &init_pid_ns);
 	inp->ih.pgid = task_pgrp_nr_ns(current, &init_pid_ns);
-	inp->ih.uid = current_fsuid();
+	inp->ih.uid = from_kuid(&init_user_ns, current_fsuid());
 
 	return (void*)inp;
 }
···
 }
 
 int venus_close(struct super_block *sb, struct CodaFid *fid, int flags,
-		vuid_t uid)
+		kuid_t uid)
 {
 	union inputArgs *inp;
 	union outputArgs *outp;
···
 	insize = SIZE(release);
 	UPARG(CODA_CLOSE);
 	
-	inp->ih.uid = uid;
+	inp->ih.uid = from_kuid(&init_user_ns, uid);
         inp->coda_close.VFid = *fid;
         inp->coda_close.flags = flags;
 

include/linux/coda_psdev.h

···
 		 const char *name, int length, int *type, 
 		 struct CodaFid *resfid);
 int venus_close(struct super_block *sb, struct CodaFid *fid, int flags,
-		vuid_t uid);
+		kuid_t uid);
 int venus_open(struct super_block *sb, struct CodaFid *fid, int flags,
 	       struct file **f);
 int venus_mkdir(struct super_block *sb, struct CodaFid *dirfid,