staging: rtl8188eu: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20200311092451.23933-2-tiwai@suse.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/core/rtw_debug.c

@@ -15,7 +15,7 @@ int proc_get_drv_version(char *page, char **start,
 {
 	int len = 0;
 
-	len += snprintf(page + len, count - len, "%s\n", DRIVERVERSION);
+	len += scnprintf(page + len, count - len, "%s\n", DRIVERVERSION);
 
 	*eof = 1;
 	return len;
@@ -86,16 +86,16 @@ int proc_get_read_reg(char *page, char **start,
 
 	switch (proc_get_read_len) {
 	case 1:
-		len += snprintf(page + len, count - len, "usb_read8(0x%x)=0x%x\n", proc_get_read_addr, usb_read8(padapter, proc_get_read_addr));
+		len += scnprintf(page + len, count - len, "usb_read8(0x%x)=0x%x\n", proc_get_read_addr, usb_read8(padapter, proc_get_read_addr));
 		break;
 	case 2:
-		len += snprintf(page + len, count - len, "usb_read16(0x%x)=0x%x\n", proc_get_read_addr, usb_read16(padapter, proc_get_read_addr));
+		len += scnprintf(page + len, count - len, "usb_read16(0x%x)=0x%x\n", proc_get_read_addr, usb_read16(padapter, proc_get_read_addr));
 		break;
 	case 4:
-		len += snprintf(page + len, count - len, "usb_read32(0x%x)=0x%x\n", proc_get_read_addr, usb_read32(padapter, proc_get_read_addr));
+		len += scnprintf(page + len, count - len, "usb_read32(0x%x)=0x%x\n", proc_get_read_addr, usb_read32(padapter, proc_get_read_addr));
 		break;
 	default:
-		len += snprintf(page + len, count - len, "error read length=%d\n", proc_get_read_len);
+		len += scnprintf(page + len, count - len, "error read length=%d\n", proc_get_read_len);
 		break;
 	}
 
@@ -138,7 +138,7 @@ int proc_get_adapter_state(char *page, char **start,
 	struct adapter *padapter = (struct adapter *)rtw_netdev_priv(dev);
 	int len = 0;
 
-	len += snprintf(page + len, count - len, "bSurpriseRemoved=%d, bDriverStopped=%d\n",
+	len += scnprintf(page + len, count - len, "bSurpriseRemoved=%d, bDriverStopped=%d\n",
 						padapter->bSurpriseRemoved, padapter->bDriverStopped);
 
 	*eof = 1;
@@ -170,11 +170,11 @@ int proc_get_best_channel(char *page, char **start,
 		}
 
 		/*  debug */
-		len += snprintf(page + len, count - len, "The rx cnt of channel %3d = %d\n",
+		len += scnprintf(page + len, count - len, "The rx cnt of channel %3d = %d\n",
 					pmlmeext->channel_set[i].ChannelNum, pmlmeext->channel_set[i].rx_count);
 	}
 
-	len += snprintf(page + len, count - len, "best_channel_24G = %d\n", best_channel_24G);
+	len += scnprintf(page + len, count - len, "best_channel_24G = %d\n", best_channel_24G);
 
 	*eof = 1;
 	return len;

drivers/staging/rtl8188eu/os_dep/ioctl_linux.c

@@ -193,12 +193,12 @@ static char *translate_scan(struct adapter *padapter,
 	/*Add basic and extended rates */
 	max_rate = 0;
 	p = custom;
-	p += snprintf(p, MAX_CUSTOM_LEN - (p - custom), " Rates (Mb/s): ");
+	p += scnprintf(p, MAX_CUSTOM_LEN - (p - custom), " Rates (Mb/s): ");
 	while (pnetwork->network.SupportedRates[i] != 0) {
 		rate = pnetwork->network.SupportedRates[i]&0x7F;
 		if (rate > max_rate)
 			max_rate = rate;
-		p += snprintf(p, MAX_CUSTOM_LEN - (p - custom),
+		p += scnprintf(p, MAX_CUSTOM_LEN - (p - custom),
 			      "%d%s ", rate >> 1, (rate & 1) ? ".5" : "");
 		i++;
 	}