crypto: algapi - use common mechanism for inheriting flags

The flag CRYPTO_ALG_ASYNC is "inherited" in the sense that when a
template is instantiated, the template will have CRYPTO_ALG_ASYNC set if
any of the algorithms it uses has CRYPTO_ALG_ASYNC set.

We'd like to add a second flag (CRYPTO_ALG_ALLOCATES_MEMORY) that gets
"inherited" in the same way.  This is difficult because the handling of
CRYPTO_ALG_ASYNC is hardcoded everywhere.  Address this by:

  - Add CRYPTO_ALG_INHERITED_FLAGS, which contains the set of flags that
    have these inheritance semantics.

  - Add crypto_algt_inherited_mask(), for use by template ->create()
    methods.  It returns any of these flags that the user asked to be
    unset and thus must be passed in the 'mask' to crypto_grab_*().

  - Also modify crypto_check_attr_type() to handle computing the 'mask'
    so that most templates can just use this.

  - Make crypto_grab_*() propagate these flags to the template instance
    being created so that templates don't have to do this themselves.

Make crypto/simd.c propagate these flags too, since it "wraps" another
algorithm, similar to a template.

Based on a patch by Mikulas Patocka <mpatocka@redhat.com>
(https://lore.kernel.org/r/alpine.LRH.2.02.2006301414580.30526@file01.intranet.prod.int.rdu2.redhat.com).

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

1 files changed, 20 insertions, 1 deletions

diff --git a/crypto/algapi.c b/crypto/algapi.c
index 92abdf675992..fdabf2675b63 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -690,6 +690,8 @@ int crypto_grab_spawn(struct crypto_spawn *spawn, struct crypto_instance *inst,
 		spawn->mask = mask;
 		spawn->next = inst->spawns;
 		inst->spawns = spawn;
+		inst->alg.cra_flags |=
+			(alg->cra_flags & CRYPTO_ALG_INHERITED_FLAGS);
 		err = 0;
 	}
 	up_write(&crypto_alg_sem);
@@ -816,7 +818,23 @@ struct crypto_attr_type *crypto_get_attr_type(struct rtattr **tb)
 }
 EXPORT_SYMBOL_GPL(crypto_get_attr_type);
 
-int crypto_check_attr_type(struct rtattr **tb, u32 type)
+/**
+ * crypto_check_attr_type() - check algorithm type and compute inherited mask
+ * @tb: the template parameters
+ * @type: the algorithm type the template would be instantiated as
+ * @mask_ret: (output) the mask that should be passed to crypto_grab_*()
+ *	      to restrict the flags of any inner algorithms
+ *
+ * Validate that the algorithm type the user requested is compatible with the
+ * one the template would actually be instantiated as.  E.g., if the user is
+ * doing crypto_alloc_shash("cbc(aes)", ...), this would return an error because
+ * the "cbc" template creates an "skcipher" algorithm, not an "shash" algorithm.
+ *
+ * Also compute the mask to use to restrict the flags of any inner algorithms.
+ *
+ * Return: 0 on success; -errno on failure
+ */
+int crypto_check_attr_type(struct rtattr **tb, u32 type, u32 *mask_ret)
 {
 	struct crypto_attr_type *algt;
 
@@ -827,6 +845,7 @@ int crypto_check_attr_type(struct rtattr **tb, u32 type)
 	if ((algt->type ^ type) & algt->mask)
 		return -EINVAL;
 
+	*mask_ret = crypto_algt_inherited_mask(algt);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(crypto_check_attr_type);