crypto: mcryptd - Check mcryptd algorithm compatibility

commit 48a992727d82cb7db076fa15d372178743b1f4cd upstream.

Algorithms not compatible with mcryptd could be spawned by mcryptd
with a direct crypto_alloc_tfm invocation using a "mcryptd(alg)" name
construct.  This causes mcryptd to crash the kernel if an arbitrary
"alg" is incompatible and not intended to be used with mcryptd.  It is
an issue if AF_ALG tries to spawn mcryptd(alg) to expose it externally.
But such algorithms must be used internally and not be exposed.

We added a check to enforce that only internal algorithms are allowed
with mcryptd at the time mcryptd is spawning an algorithm.

Link: http://marc.info/?l=linux-crypto-vger&m=148063683310477&w=2
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/crypto/mcryptd.c b/crypto/mcryptd.c
index fe5b495a434d3c1d5efc2e5b211c7d3863078726..a0ceb41d5cccc17e7f0932eca3f2dbaa71905865 100644 (file)
--- a/crypto/mcryptd.c
+++ b/crypto/mcryptd.c
@@ -258,18 +258,22 @@ out_free_inst:
        goto out;
 }
 
-static inline void mcryptd_check_internal(struct rtattr **tb, u32 *type,
+static inline bool mcryptd_check_internal(struct rtattr **tb, u32 *type,
                                          u32 *mask)
 {
        struct crypto_attr_type *algt;
 
        algt = crypto_get_attr_type(tb);
        if (IS_ERR(algt))
-               return;
-       if ((algt->type & CRYPTO_ALG_INTERNAL))
-               *type |= CRYPTO_ALG_INTERNAL;
-       if ((algt->mask & CRYPTO_ALG_INTERNAL))
-               *mask |= CRYPTO_ALG_INTERNAL;
+               return false;
+
+       *type |= algt->type & CRYPTO_ALG_INTERNAL;
+       *mask |= algt->mask & CRYPTO_ALG_INTERNAL;
+
+       if (*type & *mask & CRYPTO_ALG_INTERNAL)
+               return true;
+       else
+               return false;
 }
 
 static int mcryptd_hash_init_tfm(struct crypto_tfm *tfm)
@@ -498,7 +502,8 @@ static int mcryptd_create_hash(struct crypto_template *tmpl, struct rtattr **tb,
        u32 mask = 0;
        int err;
 
-       mcryptd_check_internal(tb, &type, &mask);
+       if (!mcryptd_check_internal(tb, &type, &mask))
+               return -EINVAL;
 
        salg = shash_attr_alg(tb[1], type, mask);
        if (IS_ERR(salg))