Re: [PATCH v4] gpio: sim: fix an invalid __free() usage

brgl
2023-09-19T07:31:42Z

On Mon, 18 Sep 2023 17:31:36 +0200, Andy Shevchenko
<andriy.shevchenko@linux.intel.com> said:
> On Mon, Sep 18, 2023 at 04:55:33PM +0200, Bartosz Golaszewski wrote:
>> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>>
>> gpio_sim_make_line_names() returns NULL or ERR_PTR() so we must not use
>> __free(kfree) on the returned address. Split this function into two, one
>> that determines the size of the "gpio-line-names" array to allocate and
>> one that actually sets the names at correct offsets. The allocation and
>> assignment of the managed pointer happens in between.
>
> ...
>
>> + unsigned int size = 0;
>>
>> list_for_each_entry(line, &bank->line_list, siblings) {
>> + if (!line->name || (line->offset >= bank->num_lines))
>> continue;
>>
>> + size = line->offset + 1;
>> }
>>
>> + return size;
>
> So, now the function iterates over all lines and returns the size of the last
> match, correct?
>
> Why not
>
> list_for_each_entry_reversed() {
> if (line->name && ())
> break;
> }
>
> return size;
>
> ?

Because the line objects are not sorted by offset. They are added at the end
of the list in the order the user creates their corresponding configfs groups.

>
> ...
>
>> +static void
>> +gpio_sim_set_line_names(struct gpio_sim_bank *bank, char **line_names)
>> +{
>> + struct gpio_sim_line *line;
>>
>> list_for_each_entry(line, &bank->line_list, siblings) {
>> - if (line->offset >= bank->num_lines)
>> + if (!line->name || (line->offset >= bank->num_lines))
>> continue;
>>
>> - if (line->name && (line->offset <= max_offset))
>> - line_names[line->offset] = line->name;
>> + line_names[line->offset] = line->name;
>> }
>> -
>> - return line_names;
>> }
>
> Can be done in the similar (I see the difference) way for the consistency with
> above.
>
> ...
>
>> + line_names_size = gpio_sim_get_line_names_size(bank);
>
>> + if (line_names_size) {
>
> Of course this can be replace with...
>
>> + line_names = kcalloc(line_names_size, sizeof(*line_names),
>> + GFP_KERNEL);
>
>> + if (!line_names)
>
> ZERO_OR_NULL_PTR() check here, but I assume we discourage use of it.

Why? There are less than 40 instances of using it in the kernel. kmalloc()
returns NULL on failure.

Bart

>
>> + return ERR_PTR(-ENOMEM);
>> +
>> + gpio_sim_set_line_names(bank, line_names);
>>
>> - if (line_names)
>> properties[prop_idx++] = PROPERTY_ENTRY_STRING_ARRAY_LEN(
>> "gpio-line-names",
>> line_names, line_names_size);
>> + }
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
>