crypto: algapi - add NEED_FALLBACK to INHERITED_FLAGS

CRYPTO_ALG_NEED_FALLBACK is handled inconsistently.  When it's requested
to be clear, some templates propagate that request to child algorithms,
while others don't.

It's apparently desired for NEED_FALLBACK to be propagated, to avoid
deadlocks where a module tries to load itself while it's being
initialized, and to avoid unnecessarily complex fallback chains where we
have e.g. cbc-aes-$driver falling back to cbc(aes-$driver) where
aes-$driver itself falls back to aes-generic, instead of cbc-aes-$driver
simply falling back to cbc(aes-generic).  There have been a number of
fixes to this effect:

commit 89027579bc ("crypto: xts - Propagate NEED_FALLBACK bit")
commit d2c2a85cfe ("crypto: ctr - Propagate NEED_FALLBACK bit")
commit e6c2e65c70 ("crypto: cbc - Propagate NEED_FALLBACK bit")

But it seems that other templates can have the same problems too.

To avoid this whack-a-mole, just add NEED_FALLBACK to INHERITED_FLAGS so
that it's always inherited.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/crypto/algapi.h

@@ -245,7 +245,8 @@ static inline u32 crypto_requires_off(struct crypto_attr_type *algt, u32 off)
  * template), these are the flags that should always be set on the "outer"
  * algorithm if any "inner" algorithm has them set.
  */
-#define CRYPTO_ALG_INHERITED_FLAGS	CRYPTO_ALG_ASYNC
+#define CRYPTO_ALG_INHERITED_FLAGS	\
+	(CRYPTO_ALG_ASYNC | CRYPTO_ALG_NEED_FALLBACK)
 
 /*
  * Given the type and mask that specify the flags restrictions on a template