boot: android: rework bootargs concatenation

Rework the bootargs concatenation allocating more accurately
the length that is needed.
Do not forget an extra byte for the null termination byte as,
in some cases, the allocation was 1 byte short.

Fixes: 86f4695b ("image: Fix Android boot image support")
Signed-off-by: Nicolas Belin <nbelin@baylibre.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Link: https://lore.kernel.org/r/20241217-fix-bootargs-concatenation-v2-3-b2fd7cf4e130@baylibre.com


Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>

boot/image-android.c

@@ -287,37 +287,40 @@ int android_image_get_kernel(const void *hdr,
 	       kernel_addr, DIV_ROUND_UP(img_data.kernel_size, 1024));
 
 	int len = 0;
+	char *bootargs = env_get("bootargs");
+
+	if (bootargs)
+		len += strlen(bootargs);
+
 	if (*img_data.kcmdline) {
 		printf("Kernel command line: %s\n", img_data.kcmdline);
-		len += strlen(img_data.kcmdline);
+		len += strlen(img_data.kcmdline) + (len ? 1 : 0); /* +1 for extra space */
 	}
 
 	if (*img_data.kcmdline_extra) {
 		printf("Kernel extra command line: %s\n", img_data.kcmdline_extra);
-		len += strlen(img_data.kcmdline_extra);
+		len += strlen(img_data.kcmdline_extra) + (len ? 1 : 0); /* +1 for extra space */
 	}
 
-	char *bootargs = env_get("bootargs");
-	if (bootargs)
-		len += strlen(bootargs);
-
-	char *newbootargs = malloc(len + 2);
+	char *newbootargs = malloc(len + 1); /* +1 for the '\0' */
 	if (!newbootargs) {
 		puts("Error: malloc in android_image_get_kernel failed!\n");
 		return -ENOMEM;
 	}
-	*newbootargs = '\0';
+	*newbootargs = '\0'; /* set to Null in case no components below are present */
 
-	if (bootargs) {
+	if (bootargs)
 		strcpy(newbootargs, bootargs);
-		strcat(newbootargs, " ");
-	}
 
-	if (*img_data.kcmdline)
+	if (*img_data.kcmdline) {
+		if (*newbootargs) /* If there is something in newbootargs, a space is needed */
+			strcat(newbootargs, " ");
 		strcat(newbootargs, img_data.kcmdline);
+	}
 
 	if (*img_data.kcmdline_extra) {
-		strcat(newbootargs, " ");
+		if (*newbootargs) /* If there is something in newbootargs, a space is needed */
+			strcat(newbootargs, " ");
 		strcat(newbootargs, img_data.kcmdline_extra);
 	}