firmware-utils: uimage_padhdr: fix Coverity issue

Fixes following issue reported by Coverity scan:

 *** CID 1452085:  Security best practices violations  (TOCTOU)
 /tools/firmware-utils/src/uimage_padhdr.c: 100 in main()
 94
 95     	if (!infname || !outfname) {
 96     		usage(argv[0]);
 97     		exit(1);
 98     	}
 99
 >>>     CID 1452085:  Security best practices violations  (TOCTOU)
 >>>     Calling function "stat" to perform check on "infname".
 100     	if (stat(infname, &statbuf) < 0) {

Fixes: a1c6a316d299 ("ramips: add support for Fon FON2601")
Signed-off-by: Petr Štetiar <ynezz@true.cz>

diff --git a/src/uimage_padhdr.c b/src/uimage_padhdr.c
index b5fb97d21ffe8cb9524f3e0ebac8be9acaa99521..d1a1efb575887868270b615b1a09bf416034f088 100644 (file)
--- a/src/uimage_padhdr.c
+++ b/src/uimage_padhdr.c
@@ -97,18 +97,6 @@ int main(int argc, char *argv[])
                exit(1);
        }
 
-       if (stat(infname, &statbuf) < 0) {
-               fprintf(stderr,
-                       "could not find input file. (errno = %d)\n", errno);
-               exit(1);
-       }
-
-       filebuf = malloc(statbuf.st_size + padsz);
-       if (!filebuf) {
-               fprintf(stderr, "buffer allocation failed\n");
-               exit(1);
-       }
-
        ifd = open(infname, O_RDONLY);
        if (ifd < 0) {
                fprintf(stderr,
@@ -123,6 +111,18 @@ int main(int argc, char *argv[])
                exit(1);
        }
 
+       if (fstat(ifd, &statbuf) < 0) {
+               fprintf(stderr,
+                       "could not fstat input file. (errno = %d)\n", errno);
+               exit(1);
+       }
+
+       filebuf = malloc(statbuf.st_size + padsz);
+       if (!filebuf) {
+               fprintf(stderr, "buffer allocation failed\n");
+               exit(1);
+       }
+
        rsz = read(ifd, filebuf, sizeof(*imgh));
        if (rsz != sizeof(*imgh)) {
                fprintf(stderr,