Thanks Pavel!
It looks really nice. I've applied it. I'll test it tonight and push
tomorrow.
I don't see any major issues with the check at all, but I have a few
comments below.
On Tue, Aug 03, 2021 at 12:00:22AM +0300, Pavel Skripkin wrote:
> +static void match_free_netdev(const char *fn, struct expression *expr, void *_arg_no)
> +{
> + struct expression *arg;
> + const char *name;
> +
> + arg = get_argument_from_call_expr(expr->args, PTR_INT(_arg_no));
> + if (!arg)
> + return;
> +
> + name = expr_to_var(arg);
> + if (!name)
> + return;
> +
> + set_state(my_id, name, NULL, &freed);
> +}
There is a new param_key API which would make this function shorter.
static void free_netdev(struct expression *expr, const char *name, struct symbol *sym, void *data)
{
set_state(my_id, name, NULL, &freed);
}
Then in the register function you'd add a hooks like this:
add_function_param_key_hook("free_netdev", &free_netdev, 0, "$", NULL);
add_function_param_key_hook("free_candev", &free_netdev, 0, "$", NULL);
Of course, you've already written your own code which works so it's
fine. But that param_key API is really the most awesome thing.
> +
> +static void match_symbol(struct expression *expr)
> +{
> + const char *parent_netdev, *name;
> + struct smatch_state *state;
> +
This hook is run for every variable so it's tempting to add a shortcut
here:
if (!has_states(my_id))
return;
> + name = expr_to_var(expr);
> + if (!name)
> + return;
> +
> + parent_netdev = get_parent_netdev_name(expr);
> + if (!parent_netdev)
> + return;
> +
> + state = get_state(my_id, parent_netdev, NULL);
> + if (state == &freed)
> + sm_error("Using %s after free_{netdev,candev}(%s);\n", name, parent_netdev);
> +}
> +
> +void check_uaf_netdev_priv(int id)
> +{
> + if (option_project != PROJ_KERNEL)
> + return;
> +
> + my_id = id;
> +
> + add_function_hook("free_netdev", &match_free_netdev, NULL);
NULL works but INT_PTR(0) is nicer. ;)
> + add_function_hook("free_candev", &match_free_netdev, NULL);
> + add_modification_hook(my_id, &ok_to_use);
> + add_hook(&match_symbol, SYM_HOOK);
> +}
Anyway, I think I will probably add the has_states() check but the
rest isn't important.
regards,
dan carpenter
