crypto: drbg - always try to free Jitter RNG instance

The Jitter RNG is unconditionally allocated as a seed source follwoing
the patch 97f2650e. Thus, the instance must always be deallocated.

Reported-by: syzbot+2e635807decef724a1fa@syzkaller.appspotmail.com
Fixes: 97f2650e ("crypto: drbg - always seeded with SP800-90B ...")
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/drbg.c

@@ -1631,10 +1631,12 @@ static int drbg_uninstantiate(struct drbg_state *drbg)
 	if (drbg->random_ready.func) {
 		del_random_ready_callback(&drbg->random_ready);
 		cancel_work_sync(&drbg->seed_work);
-		crypto_free_rng(drbg->jent);
-		drbg->jent = NULL;
 	}
 
+	if (!IS_ERR_OR_NULL(drbg->jent))
+		crypto_free_rng(drbg->jent);
+	drbg->jent = NULL;
+
 	if (drbg->d_ops)
 		drbg->d_ops->crypto_fini(drbg);
 	drbg_dealloc_state(drbg);