NFSv4: Catch and trace server filehandle encoding errors

If the server returns a filehandle with an invalid length, then trace
that, and return an EREMOTEIO error.

Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/nfs3xdr.c

···
 	if (unlikely(!p))
 		return -EIO;
 	length = be32_to_cpup(p++);
-	if (unlikely(length > NFS3_FHSIZE))
+	if (unlikely(length > NFS3_FHSIZE || length == 0))
 		goto out_toobig;
 	p = xdr_inline_decode(xdr, length);
 	if (unlikely(!p))
···
 	memcpy(fh->data, p, length);
 	return 0;
 out_toobig:
-	dprintk("NFS: file handle size (%u) too big\n", length);
+	trace_nfs_xdr_bad_filehandle(xdr, NFSERR_BADHANDLE);
 	return -E2BIG;
 }
 

fs/nfs/nfs4trace.h

···
 			), \
 			TP_ARGS(xdr, op, error))
 DEFINE_NFS4_XDR_EVENT(nfs4_xdr_status);
+DEFINE_NFS4_XDR_EVENT(nfs4_xdr_bad_filehandle);
 
 DECLARE_EVENT_CLASS(nfs4_cb_error_class,
 		TP_PROTO(

fs/nfs/nfs4xdr.c

···
 		if (unlikely(!p))
 			return -EIO;
 		len = be32_to_cpup(p);
-		if (len > NFS4_FHSIZE)
-			return -EIO;
+		if (len > NFS4_FHSIZE || len == 0) {
+			trace_nfs4_xdr_bad_filehandle(xdr, OP_READDIR,
+						      NFS4ERR_BADHANDLE);
+			return -EREMOTEIO;
+		}
 		p = xdr_inline_decode(xdr, len);
 		if (unlikely(!p))
 			return -EIO;
···
 	if (unlikely(!p))
 		return -EIO;
 	len = be32_to_cpup(p);
-	if (len > NFS4_FHSIZE)
-		return -EIO;
+	if (len > NFS4_FHSIZE || len == 0) {
+		trace_nfs4_xdr_bad_filehandle(xdr, OP_GETFH, NFS4ERR_BADHANDLE);
+		return -EREMOTEIO;
+	}
 	fh->size = len;
 	p = xdr_inline_decode(xdr, len);
 	if (unlikely(!p))

fs/nfs/nfstrace.c

···
 EXPORT_TRACEPOINT_SYMBOL_GPL(nfs_fsync_enter);
 EXPORT_TRACEPOINT_SYMBOL_GPL(nfs_fsync_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(nfs_xdr_status);
+EXPORT_TRACEPOINT_SYMBOL_GPL(nfs_xdr_bad_filehandle);

fs/nfs/nfstrace.h

···
 			), \
 			TP_ARGS(xdr, error))
 DEFINE_NFS_XDR_EVENT(nfs_xdr_status);
+DEFINE_NFS_XDR_EVENT(nfs_xdr_bad_filehandle);
 
 #endif /* _TRACE_NFS_H */