Re: [PATCH 2/3] of: Use scope based kfree() cleanups

From: Saravana Kannan
Date: Thu Apr 04 2024 - 19:16:06 EST

On Thu, Apr 4, 2024 at 7:15 AM Rob Herring <robh@xxxxxxxxxx> wrote:
>
> Use the relatively new scope based kfree() cleanup to simplify error
> handling. Doing so reduces the chances of memory leaks and simplifies
> error paths by avoiding the need for goto statements.
>
> Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
> ---
> drivers/of/base.c | 34 ++++++++--------------------------
> drivers/of/dynamic.c | 11 ++++-------
> drivers/of/resolver.c | 35 +++++++++++++----------------------
> 3 files changed, 25 insertions(+), 55 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 8856c67c466a..20603d3c9931 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -16,6 +16,7 @@
>
> #define pr_fmt(fmt) "OF: " fmt
>
> +#include <linux/cleanup.h>
> #include <linux/console.h>
> #include <linux/ctype.h>
> #include <linux/cpu.h>
> @@ -1393,8 +1394,10 @@ int of_parse_phandle_with_args_map(const struct device_node *np,
> const char *stem_name,
> int index, struct of_phandle_args *out_args)
> {
> - char *cells_name, *map_name = NULL, *mask_name = NULL;
> - char *pass_name = NULL;
> + char *cells_name __free(kfree) = kasprintf(GFP_KERNEL, "#%s-cells", stem_name);
> + char *map_name __free(kfree) = kasprintf(GFP_KERNEL, "%s-map", stem_name);
> + char *mask_name __free(kfree) = kasprintf(GFP_KERNEL, "%s-map-mask", stem_name);
> + char *pass_name __free(kfree) = kasprintf(GFP_KERNEL, "%s-map-pass-thru", stem_name);

With the scoped stuff, do these function calls need to be in the same
line we are defining these variables? If not, I'd rather that the
calls remain where they were. It feels like a lote to visually parse
and take in from a readability perspective.

> struct device_node *cur, *new = NULL;
> const __be32 *map, *mask, *pass;
> static const __be32 dummy_mask[] = { [0 ... MAX_PHANDLE_ARGS] = cpu_to_be32(~0) };
> @@ -1407,27 +1410,13 @@ int of_parse_phandle_with_args_map(const struct device_node *np,
> if (index < 0)
> return -EINVAL;
>
> - cells_name = kasprintf(GFP_KERNEL, "#%s-cells", stem_name);
> - if (!cells_name)
> + if (!cells_name || !map_name || !mask_name || !pass_name)
> return -ENOMEM;
>
> - ret = -ENOMEM;
> - map_name = kasprintf(GFP_KERNEL, "%s-map", stem_name);
> - if (!map_name)
> - goto free;
> -
> - mask_name = kasprintf(GFP_KERNEL, "%s-map-mask", stem_name);
> - if (!mask_name)
> - goto free;
> -
> - pass_name = kasprintf(GFP_KERNEL, "%s-map-pass-thru", stem_name);
> - if (!pass_name)
> - goto free;
> -
> ret = __of_parse_phandle_with_args(np, list_name, cells_name, -1, index,
> out_args);
> if (ret)
> - goto free;
> + return ret;
>
> /* Get the #<list>-cells property */
> cur = out_args->np;
> @@ -1444,8 +1433,7 @@ int of_parse_phandle_with_args_map(const struct device_node *np,
> /* Get the <list>-map property */
> map = of_get_property(cur, map_name, &map_len);
> if (!map) {
> - ret = 0;
> - goto free;
> + return 0;
> }
> map_len /= sizeof(u32);
>
> @@ -1521,12 +1509,6 @@ int of_parse_phandle_with_args_map(const struct device_node *np,
> put:
> of_node_put(cur);
> of_node_put(new);
> -free:
> - kfree(mask_name);
> - kfree(map_name);
> - kfree(cells_name);
> - kfree(pass_name);
> -
> return ret;
> }
> EXPORT_SYMBOL(of_parse_phandle_with_args_map);
> diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> index af7c57a7a25d..43f4e2c93bd2 100644
> --- a/drivers/of/dynamic.c
> +++ b/drivers/of/dynamic.c
> @@ -9,6 +9,7 @@
>
> #define pr_fmt(fmt) "OF: " fmt
>
> +#include <linux/cleanup.h>
> #include <linux/of.h>
> #include <linux/spinlock.h>
> #include <linux/slab.h>
> @@ -1019,10 +1020,9 @@ int of_changeset_add_prop_u32_array(struct of_changeset *ocs,
> const u32 *array, size_t sz)
> {
> struct property prop;
> - __be32 *val;
> - int i, ret;
> + __be32 *val __free(kfree) = kcalloc(sz, sizeof(__be32), GFP_KERNEL);
> + int i;
>
> - val = kcalloc(sz, sizeof(__be32), GFP_KERNEL);
> if (!val)
> return -ENOMEM;
>
> @@ -1032,9 +1032,6 @@ int of_changeset_add_prop_u32_array(struct of_changeset *ocs,
> prop.length = sizeof(u32) * sz;
> prop.value = (void *)val;
>
> - ret = of_changeset_add_prop_helper(ocs, np, &prop);
> - kfree(val);
> -
> - return ret;
> + return of_changeset_add_prop_helper(ocs, np, &prop);
> }
> EXPORT_SYMBOL_GPL(of_changeset_add_prop_u32_array);
> diff --git a/drivers/of/resolver.c b/drivers/of/resolver.c
> index b278ab4338ce..2780928764a4 100644
> --- a/drivers/of/resolver.c
> +++ b/drivers/of/resolver.c
> @@ -8,6 +8,7 @@
>
> #define pr_fmt(fmt) "OF: resolver: " fmt
>
> +#include <linux/cleanup.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/of.h>
> @@ -74,11 +75,11 @@ static int update_usages_of_a_phandle_reference(struct device_node *overlay,
> {
> struct device_node *refnode;
> struct property *prop;
> - char *value, *cur, *end, *node_path, *prop_name, *s;
> + char *value __free(kfree) = kmemdup(prop_fixup->value, prop_fixup->length, GFP_KERNEL);
> + char *cur, *end, *node_path, *prop_name, *s;
> int offset, len;
> int err = 0;
>
> - value = kmemdup(prop_fixup->value, prop_fixup->length, GFP_KERNEL);
> if (!value)
> return -ENOMEM;
>
> @@ -89,23 +90,19 @@ static int update_usages_of_a_phandle_reference(struct device_node *overlay,
>
> node_path = cur;
> s = strchr(cur, ':');
> - if (!s) {
> - err = -EINVAL;
> - goto err_fail;
> - }
> + if (!s)
> + return -EINVAL;
> *s++ = '\0';
>
> prop_name = s;
> s = strchr(s, ':');
> - if (!s) {
> - err = -EINVAL;
> - goto err_fail;
> - }
> + if (!s)
> + return -EINVAL;
> *s++ = '\0';
>
> err = kstrtoint(s, 10, &offset);
> if (err)
> - goto err_fail;
> + return err;
>
> refnode = __of_find_node_by_full_path(of_node_get(overlay), node_path);
> if (!refnode)
> @@ -117,22 +114,16 @@ static int update_usages_of_a_phandle_reference(struct device_node *overlay,
> }
> of_node_put(refnode);
>
> - if (!prop) {
> - err = -ENOENT;
> - goto err_fail;
> - }
> + if (!prop)
> + return -ENOENT;
>
> - if (offset < 0 || offset + sizeof(__be32) > prop->length) {
> - err = -EINVAL;
> - goto err_fail;
> - }
> + if (offset < 0 || offset + sizeof(__be32) > prop->length)
> + return -EINVAL;
>
> *(__be32 *)(prop->value + offset) = cpu_to_be32(phandle);
> }
>
> -err_fail:
> - kfree(value);
> - return err;
> + return 0;
> }
>
> /* compare nodes taking into account that 'name' strips out the @ part */

Reviewed-by: Saravana Kannan <saravanak@xxxxxxxxxx>

-Saravana