On Tue, 28 May 2024, Armin Wolf wrote:
> When reading token data from sysfs on my Inspiron 3505, the token
> locations and values are wrong. This happens because match_attribute()
> blindly assumes that all entries in da_tokens have an associated
> entry in token_attrs.
>
> This however is not true as soon as da_tokens[] contains zeroed
> token entries. Those entries are being skipped when initialising
> token_attrs, breaking the core assumption of match_attribute().
>
> Fix this by defining an extra struct for each pair of token attributes
> and use container_of() to retrieve token information.
>
> Tested on a Dell Inspiron 3050.
>
> Fixes: 33b9ca1e53b4 ("platform/x86: dell-smbios: Add a sysfs interface for SMBIOS tokens")
> Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> ---
> Changes since v1:
> - remove style changes
> - improve sizeof() usage with pointer targets
> ---
> drivers/platform/x86/dell/dell-smbios-base.c | 92 ++++++++------------
> 1 file changed, 36 insertions(+), 56 deletions(-)
>
> diff --git a/drivers/platform/x86/dell/dell-smbios-base.c b/drivers/platform/x86/dell/dell-smbios-base.c
> index e61bfaf8b5c4..86b95206cb1b 100644
> --- a/drivers/platform/x86/dell/dell-smbios-base.c
> +++ b/drivers/platform/x86/dell/dell-smbios-base.c
> @@ -11,6 +11,7 @@
> */
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> +#include <linux/container_of.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/capability.h>
> @@ -25,11 +26,16 @@ static u32 da_supported_commands;
> static int da_num_tokens;
> static struct platform_device *platform_device;
> static struct calling_interface_token *da_tokens;
> -static struct device_attribute *token_location_attrs;
> -static struct device_attribute *token_value_attrs;
> +static struct token_sysfs_data *token_entries;
> static struct attribute **token_attrs;
> static DEFINE_MUTEX(smbios_mutex);
>
> +struct token_sysfs_data {
> + struct device_attribute location_attr;
> + struct device_attribute value_attr;
> + struct calling_interface_token *token;
> +};
> +
> struct smbios_device {
> struct list_head list;
> struct device *device;
> @@ -416,47 +422,26 @@ static void __init find_tokens(const struct dmi_header *dm, void *dummy)
> }
> }
>
> -static int match_attribute(struct device *dev,
> - struct device_attribute *attr)
> -{
> - int i;
> -
> - for (i = 0; i < da_num_tokens * 2; i++) {
> - if (!token_attrs[i])
> - continue;
> - if (strcmp(token_attrs[i]->name, attr->attr.name) == 0)
> - return i/2;
> - }
> - dev_dbg(dev, "couldn't match: %s\n", attr->attr.name);
> - return -EINVAL;
> -}
> -
> static ssize_t location_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> - int i;
> + struct token_sysfs_data *data = container_of(attr, struct token_sysfs_data, location_attr);
>
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> - i = match_attribute(dev, attr);
> - if (i > 0)
> - return sysfs_emit(buf, "%08x", da_tokens[i].location);
> - return 0;
> + return sysfs_emit(buf, "%08x", data->token->location);
> }
>
> static ssize_t value_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> - int i;
> + struct token_sysfs_data *data = container_of(attr, struct token_sysfs_data, value_attr);
>
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> - i = match_attribute(dev, attr);
> - if (i > 0)
> - return sysfs_emit(buf, "%08x", da_tokens[i].value);
> - return 0;
> + return sysfs_emit(buf, "%08x", data->token->value);
> }
>
> static struct attribute_group smbios_attribute_group = {
> @@ -473,22 +458,15 @@ static int build_tokens_sysfs(struct platform_device *dev)
> {
> char *location_name;
> char *value_name;
> - size_t size;
> int ret;
> int i, j;
>
> - /* (number of tokens + 1 for null terminated */
> - size = sizeof(struct device_attribute) * (da_num_tokens + 1);
> - token_location_attrs = kzalloc(size, GFP_KERNEL);
> - if (!token_location_attrs)
> + token_entries = kcalloc(da_num_tokens, sizeof(*token_entries), GFP_KERNEL);
> + if (!token_entries)
> return -ENOMEM;
> - token_value_attrs = kzalloc(size, GFP_KERNEL);
> - if (!token_value_attrs)
> - goto out_allocate_value;
>
> /* need to store both location and value + terminator*/
> - size = sizeof(struct attribute *) * ((2 * da_num_tokens) + 1);
> - token_attrs = kzalloc(size, GFP_KERNEL);
> + token_attrs = kcalloc((2 * da_num_tokens) + 1, sizeof(*token_attrs), GFP_KERNEL);
This isn't actually required for the fix since it's in practice just a
syntatic cleanup but then it is harmful either.
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
--
i.
> if (!token_attrs)
> goto out_allocate_attrs;
>
> @@ -496,27 +474,32 @@ static int build_tokens_sysfs(struct platform_device *dev)
> /* skip empty */
> if (da_tokens[i].tokenID == 0)
> continue;
> +
> + token_entries[i].token = &da_tokens[i];
> +
> /* add location */
> location_name = kasprintf(GFP_KERNEL, "%04x_location",
> da_tokens[i].tokenID);
> if (location_name == NULL)
> goto out_unwind_strings;
> - sysfs_attr_init(&token_location_attrs[i].attr);
> - token_location_attrs[i].attr.name = location_name;
> - token_location_attrs[i].attr.mode = 0444;
> - token_location_attrs[i].show = location_show;
> - token_attrs[j++] = &token_location_attrs[i].attr;
> +
> + sysfs_attr_init(&token_entries[i].location_attr.attr);
> + token_entries[i].location_attr.attr.name = location_name;
> + token_entries[i].location_attr.attr.mode = 0444;
> + token_entries[i].location_attr.show = location_show;
> + token_attrs[j++] = &token_entries[i].location_attr.attr;
>
> /* add value */
> value_name = kasprintf(GFP_KERNEL, "%04x_value",
> da_tokens[i].tokenID);
> if (value_name == NULL)
> goto loop_fail_create_value;
> - sysfs_attr_init(&token_value_attrs[i].attr);
> - token_value_attrs[i].attr.name = value_name;
> - token_value_attrs[i].attr.mode = 0444;
> - token_value_attrs[i].show = value_show;
> - token_attrs[j++] = &token_value_attrs[i].attr;
> +
> + sysfs_attr_init(&token_entries[i].value_attr.attr);
> + token_entries[i].value_attr.attr.name = value_name;
> + token_entries[i].value_attr.attr.mode = 0444;
> + token_entries[i].value_attr.show = value_show;
> + token_attrs[j++] = &token_entries[i].value_attr.attr;
> continue;
>
> loop_fail_create_value:
> @@ -532,14 +515,12 @@ static int build_tokens_sysfs(struct platform_device *dev)
>
> out_unwind_strings:
> while (i--) {
> - kfree(token_location_attrs[i].attr.name);
> - kfree(token_value_attrs[i].attr.name);
> + kfree(token_entries[i].location_attr.attr.name);
> + kfree(token_entries[i].value_attr.attr.name);
> }
> kfree(token_attrs);
> out_allocate_attrs:
> - kfree(token_value_attrs);
> -out_allocate_value:
> - kfree(token_location_attrs);
> + kfree(token_entries);
>
> return -ENOMEM;
> }
> @@ -551,12 +532,11 @@ static void free_group(struct platform_device *pdev)
> sysfs_remove_group(&pdev->dev.kobj,
> &smbios_attribute_group);
> for (i = 0; i < da_num_tokens; i++) {
> - kfree(token_location_attrs[i].attr.name);
> - kfree(token_value_attrs[i].attr.name);
> + kfree(token_entries[i].location_attr.attr.name);
> + kfree(token_entries[i].value_attr.attr.name);
> }
> kfree(token_attrs);
> - kfree(token_value_attrs);
> - kfree(token_location_attrs);
> + kfree(token_entries);
> }
>
> static int __init dell_smbios_init(void)
> --
> 2.39.2
>
