Re: [PATCH 3/4] GPU-DRM-TILCDC: Less function calls in tilcdc_convert_slave_node() after error detection

Jyri Sarha
2016-09-22T17:05:09Z

On 09/22/16 11:33, SF Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Thu, 22 Sep 2016 10:06:50 +0200
>
> The of_node_put() function was called in some cases
> by the tilcdc_convert_slave_node() function during error handling
> even if the passed variable contained a null pointer.
>
> * Adjust jump targets according to the Linux coding style convention.
>
> * Split a condition check for resource detection failures so that
> each pointer from these function calls will be checked immediately.
>
> See also background information:
> Topic "CWE-754: Improper check for unusual or exceptional conditions"
> Link: https://cwe.mitre.org/data/definitions/754.html
>

I don't really agree with this patch. There is no harm in calling
of_node_put() with NULL as an argument and because of that there is no
point in making the function more complex and harder to maintain.

Best regards,
Jyri

> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
> drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c | 28 +++++++++++++++++-----------
> 1 file changed, 17 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c b/drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c
> index 6204405..6ee5865 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c
> @@ -209,25 +209,27 @@ void __init tilcdc_convert_slave_node(void)
> return;
>
> lcdc = of_find_matching_node(NULL, tilcdc_of_match);
> - slave = of_find_matching_node(NULL, tilcdc_slave_of_match);
> + if (!of_device_is_available(lcdc))
> + goto free_table;
>
> - if (!slave || !of_device_is_available(lcdc))
> - goto out;
> + slave = of_find_matching_node(NULL, tilcdc_slave_of_match);
> + if (!slave)
> + goto put_node_lcdc;
>
> i2c = of_parse_phandle(slave, "i2c", 0);
> if (!i2c) {
> pr_err("%s: Can't find i2c node trough phandle\n", __func__);
> - goto out;
> + goto put_node_slave;
> }
>
> overlay = tilcdc_get_overlay(&kft);
> if (!overlay)
> - goto out;
> + goto put_node_i2c;
>
> encoder = of_find_matching_node(overlay, tilcdc_tda998x_of_match);
> if (!encoder) {
> pr_err("%s: Failed to find tda998x node\n", __func__);
> - goto out;
> + goto put_node_i2c;
> }
>
> tilcdc_copy_props(slave, encoder, tilcdc_slave_props, &kft);
> @@ -238,10 +240,10 @@ void __init tilcdc_convert_slave_node(void)
> continue;
> if (!strncmp("i2c", (char *)prop->value, prop->length))
> if (tilcdc_prop_str_update(prop, i2c->full_name, &kft))
> - goto out;
> + goto put_node_fragment;
> if (!strncmp("lcdc", (char *)prop->value, prop->length))
> if (tilcdc_prop_str_update(prop, lcdc->full_name, &kft))
> - goto out;
> + goto put_node_fragment;
> }
>
> tilcdc_node_disable(slave);
> @@ -252,12 +254,16 @@ void __init tilcdc_convert_slave_node(void)
> else
> pr_info("%s: ti,tilcdc,slave node successfully converted\n",
> __func__);
> -out:
> - kfree_table_free(&kft);
> + put_node_fragment:
> + of_node_put(fragment);
> + put_node_i2c:
> of_node_put(i2c);
> + put_node_slave:
> of_node_put(slave);
> + put_node_lcdc:
> of_node_put(lcdc);
> - of_node_put(fragment);
> + free_table:
> + kfree_table_free(&kft);
> }
>
> int __init tilcdc_slave_compat_init(void)
>