ima-evm-utils: Fix reading of sigfile

Fix reading of detached IMA signature (--sigfile). Error message:

  Reading to sha1.txt.sig
  Failed to fread 147 bytes: sha1.txt.sig
  Failed reading: sha1.txt

Reported-by: Mimi Zohar <zohar@linux.ibm.com>
Fixes: 08a51e7460 ("ima-evm-utils: Fix file2bin stat and fopen relations")
Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
(cherry picked from commit 19b77c8667)

src/evmctl.c

@@ -221,7 +221,7 @@ static unsigned char *file2bin(const char *file, const char *ext, int *size)
 		fclose(fp);
 		return NULL;
 	}
-	if (fread(data, len, 1, fp) != len) {
+	if (fread(data, len, 1, fp) != 1) {
 		log_err("Failed to fread %zu bytes: %s\n", len, name);
 		fclose(fp);
 		free(data);