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crypto: algapi - add NEED_FALLBACK to INHERITED_FLAGS

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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>
This commit is contained in:
Eric Biggers 2020-07-09 23:20:39 -07:00 committed by Herbert Xu
parent 7bcb2c99f8
commit 2eb27c1193
5 changed files with 4 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
crypto/ctr.c
View file

@ -265,8 +265,6 @@ static int crypto_rfc3686_create(struct crypto_template *tmpl,
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
if (err)
return err;
mask |= crypto_requires_off(crypto_get_attr_type(tb),
CRYPTO_ALG_NEED_FALLBACK);
inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
if (!inst)

2
crypto/skcipher.c
View file

@ -943,8 +943,6 @@ struct skcipher_instance *skcipher_alloc_instance_simple(
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
if (err)
return ERR_PTR(err);
mask |= crypto_requires_off(crypto_get_attr_type(tb),
CRYPTO_ALG_NEED_FALLBACK);
inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
if (!inst)

2
crypto/xts.c
View file

@ -340,8 +340,6 @@ static int create(struct crypto_template *tmpl, struct rtattr **tb)
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
if (err)
return err;
mask |= crypto_requires_off(crypto_get_attr_type(tb),
CRYPTO_ALG_NEED_FALLBACK);
cipher_name = crypto_attr_alg_name(tb[1]);
if (IS_ERR(cipher_name))

3
include/crypto/algapi.h
View file

@ -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

4
include/linux/crypto.h
View file

@ -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