crypto: api - Fix zeroing on free

Geert Uytterhoeven pointed out that we're not zeroing all the
memory when freeing a transform.  This patch fixes it by calling
ksize to ensure that we zero everything in sight.
Reported-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/api.c

@@ -557,34 +557,34 @@ struct crypto_tfm *crypto_alloc_tfm(const char *alg_name,
 	return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(crypto_alloc_tfm);
- 
+
 /*
- *	crypto_free_tfm - Free crypto transform
+ *	crypto_destroy_tfm - Free crypto transform
+ *	@mem: Start of tfm slab
  *	@tfm: Transform to free
  *
- *	crypto_free_tfm() frees up the transform and any associated resources,
+ *	This function frees up the transform and any associated resources,
  *	then drops the refcount on the associated algorithm.
  */
-void crypto_free_tfm(struct crypto_tfm *tfm)
+void crypto_destroy_tfm(void *mem, struct crypto_tfm *tfm)
 {
 	struct crypto_alg *alg;
 	int size;
 
-	if (unlikely(!tfm))
+	if (unlikely(!mem))
 		return;
 
 	alg = tfm->__crt_alg;
-	size = sizeof(*tfm) + alg->cra_ctxsize;
+	size = ksize(mem);
 
 	if (!tfm->exit && alg->cra_exit)
 		alg->cra_exit(tfm);
 	crypto_exit_ops(tfm);
 	crypto_mod_put(alg);
-	memset(tfm, 0, size);
-	kfree(tfm);
+	memset(mem, 0, size);
+	kfree(mem);
 }
-
-EXPORT_SYMBOL_GPL(crypto_free_tfm);
+EXPORT_SYMBOL_GPL(crypto_destroy_tfm);
 
 int crypto_has_alg(const char *name, u32 type, u32 mask)
 {

include/linux/crypto.h

@@ -552,7 +552,12 @@ struct crypto_tfm *crypto_alloc_tfm(const char *alg_name,
 				    const struct crypto_type *frontend,
 				    u32 type, u32 mask);
 struct crypto_tfm *crypto_alloc_base(const char *alg_name, u32 type, u32 mask);
-void crypto_free_tfm(struct crypto_tfm *tfm);
+void crypto_destroy_tfm(void *mem, struct crypto_tfm *tfm);
+
+static inline void crypto_free_tfm(struct crypto_tfm *tfm)
+{
+	return crypto_destroy_tfm(tfm, tfm);
+}
 
 int alg_test(const char *driver, const char *alg, u32 type, u32 mask);