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 89027579bc6c ("crypto: xts - Propagate NEED_FALLBACK bit")
commit d2c2a85cfe82 ("crypto: ctr - Propagate NEED_FALLBACK bit")
commit e6c2e65c70a6 ("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>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/crypto.h b/include/linux/crypto.h
index 7cd2d00f0a05..f73f0b51e1cd 100644
--- a/include/linux/crypto.h
+++ b/include/linux/crypto.h
@@ -60,8 +60,8 @@
 #define CRYPTO_ALG_ASYNC		0x00000080
 
 /*
- * Set this bit if and only if the algorithm requires another algorithm of
- * the same type to handle corner cases.
+ * Set if the algorithm (or an algorithm which it uses) requires another
+ * algorithm of the same type to handle corner cases.
  */
 #define CRYPTO_ALG_NEED_FALLBACK	0x00000100