As explained before, there is no problem with store or load tearing on
32bit systems because the generation counter is only 32bit wide. So the
obvious solution is to only update 32 bits on a 32bit kernel:

--- a/drivers/char/random.c
+++ b/drivers/char/random.c

@@ -282,7 +282,7 @@ static void crng_reseed(struct work_stru
 	 * is ordered with the write above to base_crng.generation. Pairs with
 	 * the smp_rmb() before the syscall in the vDSO code.
 	 */
-	smp_store_release(&_vdso_rng_data.generation, next_gen + 1);
+	smp_store_release((unsigned long *)&_vdso_rng_data.generation, next_gen + 1);
 #endif
 	if (!static_branch_likely(&crng_is_ready))
 		crng_init = CRNG_READY;