sunrpc: Fix skcipher/shash conversion

The skcpiher/shash conversion introduced a number of bugs in the
sunrpc code:

1) Missing calls to skcipher_request_set_tfm lead to crashes.
2) The allocation size of shash_desc is too small which leads to
memory corruption.

Fixes: 3b5cf20cf4 ("sunrpc: Use skcipher and ahash/shash")
Reported-by: J. Bruce Fields <bfields@fieldses.org>
Tested-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

net/sunrpc/auth_gss/gss_krb5_crypto.c

@@ -78,6 +78,7 @@ krb5_encrypt(
 	memcpy(out, in, length);
 	sg_init_one(sg, out, length);
 
+	skcipher_request_set_tfm(req, tfm);
 	skcipher_request_set_callback(req, 0, NULL, NULL);
 	skcipher_request_set_crypt(req, sg, sg, length, local_iv);
 
@@ -115,6 +116,7 @@ krb5_decrypt(
 	memcpy(out, in, length);
 	sg_init_one(sg, out, length);
 
+	skcipher_request_set_tfm(req, tfm);
 	skcipher_request_set_callback(req, 0, NULL, NULL);
 	skcipher_request_set_crypt(req, sg, sg, length, local_iv);
 
@@ -946,7 +948,8 @@ krb5_rc4_setup_seq_key(struct krb5_ctx *kctx, struct crypto_skcipher *cipher,
 		return PTR_ERR(hmac);
 	}
 
-	desc = kmalloc(sizeof(*desc), GFP_KERNEL);
+	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac),
+		       GFP_KERNEL);
 	if (!desc) {
 		dprintk("%s: failed to allocate shash descriptor for '%s'\n",
 			__func__, kctx->gk5e->cksum_name);
@@ -1012,7 +1015,8 @@ krb5_rc4_setup_enc_key(struct krb5_ctx *kctx, struct crypto_skcipher *cipher,
 		return PTR_ERR(hmac);
 	}
 
-	desc = kmalloc(sizeof(*desc), GFP_KERNEL);
+	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac),
+		       GFP_KERNEL);
 	if (!desc) {
 		dprintk("%s: failed to allocate shash descriptor for '%s'\n",
 			__func__, kctx->gk5e->cksum_name);

net/sunrpc/auth_gss/gss_krb5_mech.c

@@ -451,7 +451,8 @@ context_derive_keys_rc4(struct krb5_ctx *ctx)
 		goto out_err_free_hmac;
 
 
-	desc = kmalloc(sizeof(*desc), GFP_KERNEL);
+	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac),
+		       GFP_KERNEL);
 	if (!desc) {
 		dprintk("%s: failed to allocate hash descriptor for '%s'\n",
 			__func__, ctx->gk5e->cksum_name);