rxrpc: Handle temporary errors better in rxkad security

In the rxkad security module, when we encounter a temporary error (such as
ENOMEM) from which we could conceivably recover, don't abort the
connection, but rather permit retransmission of the relevant packets to
induce a retry.

Note that I'm leaving some places that could be merged together to insert
tracing in the next patch.

Signed-off-by; David Howells <dhowells@redhat.com>

1 files changed, 40 insertions, 38 deletions

diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
index 2d5838a3dc24..988903f1dc80 100644
--- a/net/rxrpc/rxkad.c
+++ b/net/rxrpc/rxkad.c
@@ -759,16 +759,14 @@ static int rxkad_respond_to_challenge(struct rxrpc_connection *conn,
 
         _enter("{%d,%x}", conn->debug_id, key_serial(conn->params.key));
 
-        if (!conn->params.key) {
-                _leave(" = -EPROTO [no key]");
-                return -EPROTO;
-        }
+        abort_code = RX_PROTOCOL_ERROR;
+        if (!conn->params.key)
+                goto protocol_error;
 
+        abort_code = RXKADEXPIRED;
         ret = key_validate(conn->params.key);
-        if (ret < 0) {
-                *_abort_code = RXKADEXPIRED;
-                return ret;
-        }
+        if (ret < 0)
+                goto other_error;
 
         abort_code = RXKADPACKETSHORT;
         if (skb_copy_bits(skb, sizeof(struct rxrpc_wire_header),
@@ -787,8 +785,9 @@ static int rxkad_respond_to_challenge(struct rxrpc_connection *conn,
                 goto protocol_error;
 
         abort_code = RXKADLEVELFAIL;
+        ret = -EACCES;
         if (conn->params.security_level < min_level)
-                goto protocol_error;
+                goto other_error;
 
         token = conn->params.key->payload.data[0];
 
@@ -815,9 +814,10 @@ static int rxkad_respond_to_challenge(struct rxrpc_connection *conn,
         return rxkad_send_response(conn, &sp->hdr, &resp, token->kad);
 
 protocol_error:
+        ret = -EPROTO;
+other_error:
         *_abort_code = abort_code;
-        _leave(" = -EPROTO [%d]", abort_code);
-        return -EPROTO;
+        return ret;
 }
 
 /*
@@ -848,10 +848,10 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
                 switch (ret) {
                 case -EKEYEXPIRED:
                         *_abort_code = RXKADEXPIRED;
-                        goto error;
+                        goto other_error;
                 default:
                         *_abort_code = RXKADNOAUTH;
-                        goto error;
+                        goto other_error;
                 }
         }
 
@@ -860,13 +860,11 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
 
         memcpy(&iv, &conn->server_key->payload.data[2], sizeof(iv));
 
+        ret = -ENOMEM;
         req = skcipher_request_alloc(conn->server_key->payload.data[0],
                                      GFP_NOFS);
-        if (!req) {
-                *_abort_code = RXKADNOAUTH;
-                ret = -ENOMEM;
-                goto error;
-        }
+        if (!req)
+                goto temporary_error;
 
         sg_init_one(&sg[0], ticket, ticket_len);
         skcipher_request_set_callback(req, 0, NULL, NULL);
@@ -943,13 +941,13 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
         if (issue > now) {
                 *_abort_code = RXKADNOAUTH;
                 ret = -EKEYREJECTED;
-                goto error;
+                goto other_error;
         }
 
         if (issue < now - life) {
                 *_abort_code = RXKADEXPIRED;
                 ret = -EKEYEXPIRED;
-                goto error;
+                goto other_error;
         }
 
         *_expiry = issue + life;
@@ -961,16 +959,15 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
         /* get the service instance name */
         name = Z(INST_SZ);
         _debug("KIV SINST: %s", name);
-
-        ret = 0;
-error:
-        _leave(" = %d", ret);
-        return ret;
+        return 0;
 
 bad_ticket:
         *_abort_code = RXKADBADTICKET;
-        ret = -EBADMSG;
-        goto error;
+        ret = -EPROTO;
+other_error:
+        return ret;
+temporary_error:
+        return ret;
 }
 
 /*
@@ -1054,9 +1051,10 @@ static int rxkad_verify_response(struct rxrpc_connection *conn,
                 goto protocol_error;
 
         /* extract the kerberos ticket and decrypt and decode it */
+        ret = -ENOMEM;
         ticket = kmalloc(ticket_len, GFP_NOFS);
         if (!ticket)
-                return -ENOMEM;
+                goto temporary_error;
 
         abort_code = RXKADPACKETSHORT;
         if (skb_copy_bits(skb, sizeof(struct rxrpc_wire_header),
@@ -1064,12 +1062,9 @@ static int rxkad_verify_response(struct rxrpc_connection *conn,
                 goto protocol_error_free;
 
         ret = rxkad_decrypt_ticket(conn, ticket, ticket_len, &session_key,
-                                   &expiry, &abort_code);
-        if (ret < 0) {
-                *_abort_code = abort_code;
-                kfree(ticket);
-                return ret;
-        }
+                                   &expiry, _abort_code);
+        if (ret < 0)
+                goto temporary_error_free;
 
         /* use the session key from inside the ticket to decrypt the
          * response */
@@ -1123,10 +1118,8 @@ static int rxkad_verify_response(struct rxrpc_connection *conn,
          * this the connection security can be handled in exactly the same way
          * as for a client connection */
         ret = rxrpc_get_server_data_key(conn, &session_key, expiry, kvno);
-        if (ret < 0) {
-                kfree(ticket);
-                return ret;
-        }
+        if (ret < 0)
+                goto temporary_error_free;
 
         kfree(ticket);
         _leave(" = 0");
@@ -1140,6 +1133,15 @@ protocol_error:
         *_abort_code = abort_code;
         _leave(" = -EPROTO [%d]", abort_code);
         return -EPROTO;
+
+temporary_error_free:
+        kfree(ticket);
+temporary_error:
+        /* Ignore the response packet if we got a temporary error such as
+         * ENOMEM.  We just want to send the challenge again.  Note that we
+         * also come out this way if the ticket decryption fails.
+         */
+        return ret;
 }
 
 /*