s390/ctcm: Convert sprintf/snprintf to scnprintf

This LWN article explains the why scnprintf is preferred over snprintf
in general
https://lwn.net/Articles/69419/
Ie. snprintf() returns what *would* be the resulting length, while
scnprintf() returns the actual length.

Note that ctcm_print_statistics() writes the data into the kernel log
and is therefore not suitable for sysfs_emit(). Observable behavior is
not changed, as there may be dependencies.

Reviewed-by: Alexandra Winter <[e-mail]>
Signed-off-by: Thorsten Winkler <[e-mail]>
Signed-off-by: Alexandra Winter <[e-mail]>
Signed-off-by: Paolo Abeni <[e-mail]>

drivers/s390/net/ctcm_dbug.c

···
 	if (!debug_level_enabled(ctcm_dbf[dbf_nix].id, level))
 		return;
 	va_start(args, fmt);
-	vsnprintf(dbf_txt_buf, sizeof(dbf_txt_buf), fmt, args);
+	vscnprintf(dbf_txt_buf, sizeof(dbf_txt_buf), fmt, args);
 	va_end(args);
 
 	debug_text_event(ctcm_dbf[dbf_nix].id, level, dbf_txt_buf);

drivers/s390/net/ctcm_main.c

···
 					goto nomem_return;
 
 	ch->cdev = cdev;
-	snprintf(ch->id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev->dev));
+	scnprintf(ch->id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev->dev));
 	ch->type = type;
 
 	/*
···
 
 	type = get_channel_type(&cdev0->id);
 
-	snprintf(read_id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev0->dev));
-	snprintf(write_id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev1->dev));
+	scnprintf(read_id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev0->dev));
+	scnprintf(write_id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev1->dev));
 
 	ret = add_channel(cdev0, type, priv);
 	if (ret) {

drivers/s390/net/ctcm_main.h

···
 #define CTCM_PROTO_MPC		4
 #define CTCM_PROTO_MAX		4
 
+#define CTCM_STATSIZE_LIMIT	64
 #define CTCM_BUFSIZE_LIMIT	65535
 #define CTCM_BUFSIZE_DEFAULT	32768
 #define MPC_BUFSIZE_DEFAULT	CTCM_BUFSIZE_LIMIT

drivers/s390/net/ctcm_mpc.c

···
 
 	for (ct = 0; ct < len; ct++, ptr++, rptr++) {
 		if (sw == 0) {
-			sprintf(addr, "%16.16llx", (__u64)rptr);
+			scnprintf(addr, sizeof(addr), "%16.16llx", (__u64)rptr);
 
-			sprintf(boff, "%4.4X", (__u32)ct);
+			scnprintf(boff, sizeof(boff), "%4.4X", (__u32)ct);
 			bhex[0] = '\0';
 			basc[0] = '\0';
 		}
···
 		if (sw == 8)
 			strcat(bhex, "	");
 
-		sprintf(tbuf, "%2.2llX", (__u64)*ptr);
+		scnprintf(tbuf, sizeof(tbuf), "%2.2llX", (__u64)*ptr);
 
 		tbuf[2] = '\0';
 		strcat(bhex, tbuf);
···
 			continue;
 		if ((strcmp(duphex, bhex)) != 0) {
 			if (dup != 0) {
-				sprintf(tdup,
-					"Duplicate as above to %s", addr);
+				scnprintf(tdup, sizeof(tdup),
+					  "Duplicate as above to %s", addr);
 				ctcm_pr_debug("		       --- %s ---\n",
 						tdup);
 			}
···
 			strcat(basc, " ");
 		}
 		if (dup != 0) {
-			sprintf(tdup, "Duplicate as above to %s", addr);
+			scnprintf(tdup, sizeof(tdup),
+				  "Duplicate as above to %s", addr);
 			ctcm_pr_debug("		       --- %s ---\n", tdup);
 		}
 		ctcm_pr_debug("   %s (+%s) : %s  [%s]\n",
 					addr, boff, bhex, basc);
 	} else {
 		if (dup >= 1) {
-			sprintf(tdup, "Duplicate as above to %s", addr);
+			scnprintf(tdup, sizeof(tdup),
+				  "Duplicate as above to %s", addr);
 			ctcm_pr_debug("		       --- %s ---\n", tdup);
 		}
 		if (dup != 0) {
···
 	struct net_device *dev;
 	struct ctcm_priv *priv;
 
-	sprintf(device, "%s%i", MPC_DEVICE_NAME, port_num);
+	scnprintf(device, sizeof(device), "%s%i", MPC_DEVICE_NAME, port_num);
 
 	dev = __dev_get_by_name(&init_net, device);
 

drivers/s390/net/ctcm_sysfs.c

···
 		return;
 	p = sbuf;
 
-	p += sprintf(p, "  Device FSM state: %s\n",
-		     fsm_getstate_str(priv->fsm));
-	p += sprintf(p, "  RX channel FSM state: %s\n",
-		     fsm_getstate_str(priv->channel[CTCM_READ]->fsm));
-	p += sprintf(p, "  TX channel FSM state: %s\n",
-		     fsm_getstate_str(priv->channel[CTCM_WRITE]->fsm));
-	p += sprintf(p, "  Max. TX buffer used: %ld\n",
-		     priv->channel[WRITE]->prof.maxmulti);
-	p += sprintf(p, "  Max. chained SKBs: %ld\n",
-		     priv->channel[WRITE]->prof.maxcqueue);
-	p += sprintf(p, "  TX single write ops: %ld\n",
-		     priv->channel[WRITE]->prof.doios_single);
-	p += sprintf(p, "  TX multi write ops: %ld\n",
-		     priv->channel[WRITE]->prof.doios_multi);
-	p += sprintf(p, "  Netto bytes written: %ld\n",
-		     priv->channel[WRITE]->prof.txlen);
-	p += sprintf(p, "  Max. TX IO-time: %u\n",
-		     jiffies_to_usecs(priv->channel[WRITE]->prof.tx_time));
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Device FSM state: %s\n",
+		       fsm_getstate_str(priv->fsm));
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  RX channel FSM state: %s\n",
+		       fsm_getstate_str(priv->channel[CTCM_READ]->fsm));
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  TX channel FSM state: %s\n",
+		       fsm_getstate_str(priv->channel[CTCM_WRITE]->fsm));
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Max. TX buffer used: %ld\n",
+		       priv->channel[WRITE]->prof.maxmulti);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Max. chained SKBs: %ld\n",
+		       priv->channel[WRITE]->prof.maxcqueue);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  TX single write ops: %ld\n",
+		       priv->channel[WRITE]->prof.doios_single);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  TX multi write ops: %ld\n",
+		       priv->channel[WRITE]->prof.doios_multi);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Netto bytes written: %ld\n",
+		       priv->channel[WRITE]->prof.txlen);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Max. TX IO-time: %u\n",
+		       jiffies_to_usecs(priv->channel[WRITE]->prof.tx_time));
 
 	printk(KERN_INFO "Statistics for %s:\n%s",
 				priv->channel[CTCM_WRITE]->netdev->name, sbuf);