caif: Fix for a race in socket transmit with flow control.

Kill faulty checks on flow-off leading to connection drop at race conditions.
caif_socket checks for flow-on before transmitting and goes to sleep or
return -EAGAIN upon flow stop. Remove faulty subsequent checks on flow-off
leading to connection drop. Also fix memory leaks on some of the errors paths.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/caif/cfdbgl.c

@@ -41,8 +41,10 @@ static int cfdbgl_transmit(struct cflayer *layr, struct cfpkt *pkt)
 	struct caif_payload_info *info;
 	int ret;
 
-	if (!cfsrvl_ready(service, &ret))
+	if (!cfsrvl_ready(service, &ret)) {
+		cfpkt_destroy(pkt);
 		return ret;
+	}
 
 	/* Add info for MUX-layer to route the packet out */
 	info = cfpkt_info(pkt);

net/caif/cfdgml.c

@@ -86,12 +86,17 @@ static int cfdgml_transmit(struct cflayer *layr, struct cfpkt *pkt)
 	struct caif_payload_info *info;
 	struct cfsrvl *service = container_obj(layr);
 	int ret;
-	if (!cfsrvl_ready(service, &ret))
+
+	if (!cfsrvl_ready(service, &ret)) {
+		cfpkt_destroy(pkt);
 		return ret;
+	}
 
 	/* STE Modem cannot handle more than 1500 bytes datagrams */
-	if (cfpkt_getlen(pkt) > DGM_MTU)
+	if (cfpkt_getlen(pkt) > DGM_MTU) {
+		cfpkt_destroy(pkt);
 		return -EMSGSIZE;
+	}
 
 	cfpkt_add_head(pkt, &zero, 3);
 	packet_type = 0x08; /* B9 set - UNCLASSIFIED */

net/caif/cfrfml.c

@@ -184,6 +184,11 @@ out:
 					rfml->serv.dev_info.id);
 	}
 	spin_unlock(&rfml->sync);
+
+	if (unlikely(err == -EAGAIN))
+		/* It is not possible to recover after drop of a fragment */
+		err = -EIO;
+
 	return err;
 }
 
@@ -218,7 +223,7 @@ static int cfrfml_transmit(struct cflayer *layr, struct cfpkt *pkt)
 	caif_assert(layr->dn->transmit != NULL);
 
 	if (!cfsrvl_ready(&rfml->serv, &err))
-		return err;
+		goto out;
 
 	err = -EPROTO;
 	if (cfpkt_getlen(pkt) <= RFM_HEAD_SIZE-1)
@@ -251,8 +256,11 @@ static int cfrfml_transmit(struct cflayer *layr, struct cfpkt *pkt)
 
 		err = cfrfml_transmit_segment(rfml, frontpkt);
 
-		if (err != 0)
+		if (err != 0) {
+			frontpkt = NULL;
 			goto out;
+		}
+
 		frontpkt = rearpkt;
 		rearpkt = NULL;
 
@@ -286,19 +294,8 @@ out:
 		if (rearpkt)
 			cfpkt_destroy(rearpkt);
 
-		if (frontpkt && frontpkt != pkt) {
-
+		if (frontpkt)
 			cfpkt_destroy(frontpkt);
-			/*
-			 * Socket layer will free the original packet,
-			 * but this packet may already be sent and
-			 * freed. So we have to return 0 in this case
-			 * to avoid socket layer to re-free this packet.
-			 * The return of shutdown indication will
-			 * cause connection to be invalidated anyhow.
-			 */
-			err = 0;
-		}
 	}
 
 	return err;

net/caif/cfsrvl.c

@@ -174,15 +174,11 @@ void cfsrvl_init(struct cfsrvl *service,
 
 bool cfsrvl_ready(struct cfsrvl *service, int *err)
 {
-	if (service->open && service->modem_flow_on && service->phy_flow_on)
-		return true;
 	if (!service->open) {
 		*err = -ENOTCONN;
 		return false;
 	}
-	caif_assert(!(service->modem_flow_on && service->phy_flow_on));
-	*err = -EAGAIN;
-	return false;
+	return true;
 }
 
 u8 cfsrvl_getphyid(struct cflayer *layer)

net/caif/cfutill.c

@@ -84,8 +84,11 @@ static int cfutill_transmit(struct cflayer *layr, struct cfpkt *pkt)
 	caif_assert(layr != NULL);
 	caif_assert(layr->dn != NULL);
 	caif_assert(layr->dn->transmit != NULL);
-	if (!cfsrvl_ready(service, &ret))
+
+	if (!cfsrvl_ready(service, &ret)) {
+		cfpkt_destroy(pkt);
 		return ret;
+	}
 
 	cfpkt_add_head(pkt, &zero, 1);
 	/* Add info for MUX-layer to route the packet out. */

net/caif/cfvidl.c

@@ -50,8 +50,12 @@ static int cfvidl_transmit(struct cflayer *layr, struct cfpkt *pkt)
 	struct caif_payload_info *info;
 	u32 videoheader = 0;
 	int ret;
-	if (!cfsrvl_ready(service, &ret))
+
+	if (!cfsrvl_ready(service, &ret)) {
+		cfpkt_destroy(pkt);
 		return ret;
+	}
+
 	cfpkt_add_head(pkt, &videoheader, 4);
 	/* Add info for MUX-layer to route the packet out */
 	info = cfpkt_info(pkt);