brcmfmac: Do not use strcpy and strcat

Commit "c1b2053 brcmfmac: Make firmware path a module parameter"
introduced use of strcpy and strcat. The strcpy and strcat require
using null terminated strings and can cause out-of-bounds memory
access and subsequent corruption. This patch replaces these by
strncpy and strncat respectively to assure array boundaries are
not crossed.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Signed-off-by: Daniel Kim <dekim@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c

@@ -670,6 +670,8 @@ static int brcmf_sdio_get_fwnames(struct brcmf_chip *ci,
 				  struct brcmf_sdio_dev *sdiodev)
 {
 	int i;
+	uint fw_len, nv_len;
+	char end;
 
 	for (i = 0; i < ARRAY_SIZE(brcmf_fwname_data); i++) {
 		if (brcmf_fwname_data[i].chipid == ci->chip &&
@@ -682,16 +684,25 @@ static int brcmf_sdio_get_fwnames(struct brcmf_chip *ci,
 		return -ENODEV;
 	}
 
+	fw_len = sizeof(sdiodev->fw_name) - 1;
+	nv_len = sizeof(sdiodev->nvram_name) - 1;
 	/* check if firmware path is provided by module parameter */
 	if (brcmf_firmware_path[0] != '\0') {
-		if (brcmf_firmware_path[strlen(brcmf_firmware_path) - 1] != '/')
-			strcat(brcmf_firmware_path, "/");
-
-		strcpy(sdiodev->fw_name, brcmf_firmware_path);
-		strcpy(sdiodev->nvram_name, brcmf_firmware_path);
+		strncpy(sdiodev->fw_name, brcmf_firmware_path, fw_len);
+		strncpy(sdiodev->nvram_name, brcmf_firmware_path, nv_len);
+		fw_len -= strlen(sdiodev->fw_name);
+		nv_len -= strlen(sdiodev->nvram_name);
+
+		end = brcmf_firmware_path[strlen(brcmf_firmware_path) - 1];
+		if (end != '/') {
+			strncat(sdiodev->fw_name, "/", fw_len);
+			strncat(sdiodev->nvram_name, "/", nv_len);
+			fw_len--;
+			nv_len--;
+		}
 	}
-	strcat(sdiodev->fw_name, brcmf_fwname_data[i].bin);
-	strcat(sdiodev->nvram_name, brcmf_fwname_data[i].nv);
+	strncat(sdiodev->fw_name, brcmf_fwname_data[i].bin, fw_len);
+	strncat(sdiodev->nvram_name, brcmf_fwname_data[i].nv, nv_len);
 
 	return 0;
 }