rxrpc: Fix unhandled errors in rxgk_verify_packet_integrity()

rxgk_verify_packet_integrity() may get more errors than just -EPROTO from
rxgk_verify_mic_skb(). Pretty much anything other than -ENOMEM constitutes
an unrecoverable error. In the case of -ENOMEM, we can just drop the
packet and wait for a retransmission.

Similar happens with rxgk_decrypt_skb() and its callers.

Fix rxgk_decrypt_skb() or rxgk_verify_mic_skb() to return a greater variety
of abort codes and fix their callers to abort the connection on any error
apart from -ENOMEM.

Also preclear the variables used to hold the abort code returned from
rxgk_decrypt_skb() or rxgk_verify_mic_skb() to eliminate uninitialised
variable warnings.

Fixes: 9d1d2b59341f ("rxrpc: rxgk: Implement the yfs-rxgk security class (GSSAPI)")
Reported-by: Dan Carpenter <[e-mail]>
Closes: https://lists.infradead.org/pipermail/linux-afs/2025-April/009739.html
Closes: https://lists.infradead.org/pipermail/linux-afs/2025-April/009740.html
Signed-off-by: David Howells <[e-mail]>
cc: Marc Dionne <[e-mail]>
cc: [e-mail]
Reviewed-by: Simon Horman <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/rxrpc/rxgk.c

···
 	struct krb5_buffer metadata;
 	unsigned int offset = sp->offset, len = sp->len;
 	size_t data_offset = 0, data_len = len;
-	u32 ac;
+	u32 ac = 0;
 	int ret = -ENOMEM;
 
 	_enter("");
···
 	ret = rxgk_verify_mic_skb(gk->krb5, gk->rx_Kc, &metadata,
 				  skb, &offset, &len, &ac);
 	kfree(hdr);
-	if (ret == -EPROTO) {
-		rxrpc_abort_eproto(call, skb, ac,
-				   rxgk_abort_1_verify_mic_eproto);
+	if (ret < 0) {
+		if (ret != -ENOMEM)
+			rxrpc_abort_eproto(call, skb, ac,
+					   rxgk_abort_1_verify_mic_eproto);
 	} else {
 		sp->offset = offset;
 		sp->len = len;
···
 	struct rxgk_header hdr;
 	unsigned int offset = sp->offset, len = sp->len;
 	int ret;
-	u32 ac;
+	u32 ac = 0;
 
 	_enter("");
 
 	ret = rxgk_decrypt_skb(gk->krb5, gk->rx_enc, skb, &offset, &len, &ac);
-	if (ret == -EPROTO)
-		rxrpc_abort_eproto(call, skb, ac, rxgk_abort_2_decrypt_eproto);
-	if (ret < 0)
+	if (ret < 0) {
+		if (ret != -ENOMEM)
+			rxrpc_abort_eproto(call, skb, ac, rxgk_abort_2_decrypt_eproto);
 		goto error;
+	}
 
 	if (len < sizeof(hdr)) {
 		ret = rxrpc_abort_eproto(call, skb, RXGK_PACKETSHORT,

net/rxrpc/rxgk_app.c

···
 	struct key *server_key;
 	unsigned int ticket_offset, ticket_len;
 	u32 kvno, enctype;
-	int ret, ec;
+	int ret, ec = 0;
 
 	struct {
 		__be32 kvno;
···
 			       &ticket_offset, &ticket_len, &ec);
 	crypto_free_aead(token_enc);
 	token_enc = NULL;
-	if (ret < 0)
-		return rxrpc_abort_conn(conn, skb, ec, ret,
-					rxgk_abort_resp_tok_dec);
+	if (ret < 0) {
+		if (ret != -ENOMEM)
+			return rxrpc_abort_conn(conn, skb, ec, ret,
+						rxgk_abort_resp_tok_dec);
+	}
 
 	ret = conn->security->default_decode_ticket(conn, skb, ticket_offset,
 						    ticket_len, _key);

net/rxrpc/rxgk_common.h

···
 		*_offset += offset;
 		*_len = len;
 		break;
+	case -EBADMSG: /* Checksum mismatch. */
 	case -EPROTO:
-	case -EBADMSG:
 		*_error_code = RXGK_SEALEDINCON;
 		break;
+	case -EMSGSIZE:
+		*_error_code = RXGK_PACKETSHORT;
+		break;
+	case -ENOPKG: /* Would prefer RXGK_BADETYPE, but not available for YFS. */
 	default:
+		*_error_code = RXGK_INCONSISTENCY;
 		break;
 	}
 
···
 		*_offset += offset;
 		*_len = len;
 		break;
+	case -EBADMSG: /* Checksum mismatch */
 	case -EPROTO:
-	case -EBADMSG:
 		*_error_code = RXGK_SEALEDINCON;
 		break;
+	case -EMSGSIZE:
+		*_error_code = RXGK_PACKETSHORT;
+		break;
+	case -ENOPKG: /* Would prefer RXGK_BADETYPE, but not available for YFS. */
 	default:
+		*_error_code = RXGK_INCONSISTENCY;
 		break;
 	}