[PATCH] mdev: add NULL-checks in clean_up_cur_rule()

[Kang-Che Sung]

Maks Mishin <maks.mishinfz at gmail.com> 於 2024年8月19日 星期一寫道：
> The function clean_up_cur_rule() calls in the loop, which can lead to
> double-free of pointers `G.cur_rule.envvar` and `G.cur_rule.ren_mov`.
> Added NULL checks and NULL assignment after free for correct checks.
>

> -       free(G.cur_rule.envvar);
> -       free(G.cur_rule.ren_mov);
> +       if (G.cur_rule.envvar != NULL) {
> +               free(G.cur_rule.envvar);
> +               G.cur_rule.envvar = NULL;
> +       }
> +       if (G.cur_rule.ren_mov != NULL) {
> +               free(G.cur_rule.ren_mov);
> +               G.cur_rule.ren_mov = NULL;
> +       }
> +

libc free() function should do no-op if the argument is NULL. Thus the
check for NULL conditionals may be removed.
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