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>

diff --git a/boot/image-android.c b/boot/image-android.c
index 362a5c7435a3a8bcf7b674b96e31069a91a892b5..61ac312db7ad9ba6c55727469dd4ded61824c67c 100644 (file)
--- a/boot/image-android.c
+++ b/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);
        }