MPILIB: Add a missing ENOMEM check

Add a missing ENOMEM check.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

lib/mpi/mpicoder.c

@@ -255,6 +255,8 @@ void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
 	if (!n)
 		n++;		/* avoid zero length allocation */
 	p = buffer = kmalloc(n, GFP_KERNEL);
+	if (!p)
+		return NULL;
 
 	for (i = a->nlimbs - 1; i >= 0; i--) {
 		alimb = a->d[i];