kwbimage: check return value of image_get_csk_index

image_get_csk_index() may return -1 in case of an error. Don't use this
value as index.

This resolves Coverity CID 338488
Memory - illegal accesses  (NEGATIVE_RETURNS)

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Pali Rohár <pali@kernel.org>

diff --git a/tools/kwbimage.c b/tools/kwbimage.c
index b269488..aa865cc 100644 (file)
--- a/tools/kwbimage.c
+++ b/tools/kwbimage.c
@@ -1087,7 +1087,7 @@ int kwb_sign_csk_with_kak(struct image_tool_params *params,
        int csk_idx = image_get_csk_index();
        struct sig_v1 tmp_sig;
 
-       if (csk_idx >= 16) {
+       if (csk_idx < 0 || csk_idx > 15) {
                fprintf(stderr, "Invalid CSK index %d\n", csk_idx);
                return 1;
        }