Avoid calling rw_destroy() on uninitialized rwlock

First the function `memset(&key, 0, ...)` but
any call to "goto error;" would call zio_crypt_key_destroy(key) which
calls `rw_destroy()`. The `rw_init()` is moved up to be right after the
memset. This way the rwlock can be released.

The ctx does allocate memory, but that is handled by the memset to 0
and icp skips NULL ptrs.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Richard Yao <[email protected]>
Signed-off-by: Jorgen Lundman <[email protected]>
Closes #13976

module/os/linux/zfs/zio_crypt.c

@@ -249,6 +249,7 @@ zio_crypt_key_init(uint64_t crypt, zio_crypt_key_t *key)
 #pragma GCC diagnostic pop
 #endif
 	memset(key, 0, sizeof (zio_crypt_key_t));
+	rw_init(&key->zk_salt_lock, NULL, RW_DEFAULT, NULL);
 
 	/* fill keydata buffers and salt with random data */
 	ret = random_get_bytes((uint8_t *)&key->zk_guid, sizeof (uint64_t));
@@ -302,7 +303,6 @@ zio_crypt_key_init(uint64_t crypt, zio_crypt_key_t *key)
 	key->zk_crypt = crypt;
 	key->zk_version = ZIO_CRYPT_KEY_CURRENT_VERSION;
 	key->zk_salt_count = 0;
-	rw_init(&key->zk_salt_lock, NULL, RW_DEFAULT, NULL);
 
 	return (0);