crypto: adiantum - initialize crypto_spawn::inst

crypto_grab_*() doesn't set crypto_spawn::inst, so templates must set it
beforehand.  Otherwise it will be left NULL, which causes a crash in
certain cases where algorithms are dynamically loaded/unloaded.  E.g.
with CONFIG_CRYPTO_CHACHA20_X86_64=m, the following caused a crash:

    insmod chacha-x86_64.ko
    python -c 'import socket; socket.socket(socket.AF_ALG, 5, 0).bind(("skcipher", "adiantum(xchacha12,aes)"))'
    rmmod chacha-x86_64.ko
    python -c 'import socket; socket.socket(socket.AF_ALG, 5, 0).bind(("skcipher", "adiantum(xchacha12,aes)"))'

Fixes: 059c2a4d ("crypto: adiantum - add Adiantum support")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/adiantum.c

@@ -539,6 +539,8 @@ static int adiantum_create(struct crypto_template *tmpl, struct rtattr **tb)
 	ictx = skcipher_instance_ctx(inst);
 
 	/* Stream cipher, e.g. "xchacha12" */
+	crypto_set_skcipher_spawn(&ictx->streamcipher_spawn,
+				  skcipher_crypto_instance(inst));
 	err = crypto_grab_skcipher(&ictx->streamcipher_spawn, streamcipher_name,
 				   0, crypto_requires_sync(algt->type,
 							   algt->mask));
@@ -547,6 +549,8 @@ static int adiantum_create(struct crypto_template *tmpl, struct rtattr **tb)
 	streamcipher_alg = crypto_spawn_skcipher_alg(&ictx->streamcipher_spawn);
 
 	/* Block cipher, e.g. "aes" */
+	crypto_set_spawn(&ictx->blockcipher_spawn,
+			 skcipher_crypto_instance(inst));
 	err = crypto_grab_spawn(&ictx->blockcipher_spawn, blockcipher_name,
 				CRYPTO_ALG_TYPE_CIPHER, CRYPTO_ALG_TYPE_MASK);
 	if (err)