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From 9510aa4aebf32678884f55ae251e54012a354ed1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alice=20=E2=9C=A8=F0=9F=8C=99=20Luna?= <alice@liquidnya.dev>
Date: Sat, 22 Aug 2026 16:26:42 +0200
Subject: [PATCH] Use sysfs_emit and field width specifier '*'
This fixes the build due to strncpy being removed from the kernel 7.2
and also makes the code more readable,
since the handling of buffer overflows id done by sysfs_emit.
Note that the documentation about reading attributes says:
> New implementations of show() methods should only use sysfs_emit()
> or sysfs_emit_at() when formatting the value to be returned to user space.
See: https://docs.kernel.org/filesystems/sysfs.html#reading-writing-attribute-data
from kernel 7.2.0, last revised 16 August 2011.
This change also uses the field width specifier '*' for add_uevent_var calls.
---
ddcci/ddcci.c | 153 +++++++++++++++++---------------------------------
1 file changed, 50 insertions(+), 103 deletions(-)
diff --git a/ddcci/ddcci.c b/ddcci/ddcci.c
index 6b41eab..76a1cd3 100644
--- a/ddcci/ddcci.c
+++ b/ddcci/ddcci.c
@@ -735,154 +735,101 @@ static ssize_t ddcci_attr_capabilities_show(struct device *dev,
char *buf)
{
struct ddcci_device *device = ddcci_verify_device(dev);
- ssize_t ret = -ENOENT;
- size_t len;
if (likely(device != NULL)) {
- len = device->capabilities_len;
- if (unlikely(len > PAGE_SIZE))
- len = PAGE_SIZE;
- if (len == 0) {
- ret = len;
- } else {
- memcpy(buf, device->capabilities, len);
- if (likely(len < PAGE_SIZE)) {
- buf[len] = '\n';
- ret = len+1;
- }
- }
- }
+ if (device->capabilities_len == 0)
+ return 0;
- return ret;
+ return sysfs_emit(buf, "%.*s\n", (int)device->capabilities_len, device->capabilities);
+ }
+ return -ENOENT;
}
static ssize_t ddcci_attr_prot_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct ddcci_device *device = ddcci_verify_device(dev);
- ssize_t ret = -ENOENT;
- size_t len;
if (likely(device != NULL)) {
- len = strnlen(device->prot, sizeof(device->prot));
- strncpy(buf, device->prot, PAGE_SIZE);
- if (len == 0) {
- ret = len;
- } else if (likely(len < PAGE_SIZE)) {
- buf[len] = '\n';
- ret = len+1;
- } else {
- ret = PAGE_SIZE;
- }
+ if (device->prot[0] == '\0')
+ return 0;
+
+ return sysfs_emit(buf, "%.*s\n", (int)sizeof(device->prot), device->prot);
}
- return ret;
+ return -ENOENT;
}
static ssize_t ddcci_attr_type_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct ddcci_device *device = ddcci_verify_device(dev);
- ssize_t ret = -ENOENT;
- size_t len;
if (likely(device != NULL)) {
- len = strnlen(device->type, sizeof(device->type));
- strncpy(buf, device->type, PAGE_SIZE);
- if (len == 0) {
- ret = len;
- } else if (likely(len < PAGE_SIZE)) {
- buf[len] = '\n';
- ret = len+1;
- } else {
- ret = PAGE_SIZE;
- }
+ if (device->type[0] == '\0')
+ return 0;
+
+ return sysfs_emit(buf, "%.*s\n", (int)sizeof(device->type), device->type);
}
- return ret;
+ return -ENOENT;
}
static ssize_t ddcci_attr_model_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct ddcci_device *device = ddcci_verify_device(dev);
- ssize_t ret = -ENOENT;
- size_t len;
if (likely(device != NULL)) {
- len = strnlen(device->model, sizeof(device->model));
- strncpy(buf, device->model, PAGE_SIZE);
- if (len == 0) {
- ret = len;
- } else if (likely(len < PAGE_SIZE)) {
- buf[len] = '\n';
- ret = len+1;
- } else {
- ret = PAGE_SIZE;
- }
+ if (device->model[0] == '\0')
+ return 0;
+
+ return sysfs_emit(buf, "%.*s\n", (int)sizeof(device->model), device->model);
}
- return ret;
+ return -ENOENT;
}
static ssize_t ddcci_attr_vendor_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct ddcci_device *device = ddcci_verify_device(dev);
- ssize_t ret = -ENOENT;
- size_t len;
if (likely(device != NULL)) {
- len = strnlen(device->vendor, sizeof(device->vendor));
- strncpy(buf, device->vendor, PAGE_SIZE);
- if (len == 0) {
- ret = len;
- } else if (likely(len < PAGE_SIZE)) {
- buf[len] = '\n';
- ret = len+1;
- } else {
- ret = PAGE_SIZE;
- }
+ if (device->vendor[0] == '\0')
+ return 0;
+
+ return sysfs_emit(buf, "%.*s\n", (int)sizeof(device->vendor), device->vendor);
}
- return ret;
+ return -ENOENT;
}
static ssize_t ddcci_attr_module_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct ddcci_device *device = ddcci_verify_device(dev);
- ssize_t ret = -ENOENT;
- size_t len;
if (likely(device != NULL)) {
- len = strnlen(device->module, sizeof(device->module));
- strncpy(buf, device->module, PAGE_SIZE);
- if (len == 0) {
- ret = len;
- } else if (likely(len < PAGE_SIZE)) {
- buf[len] = '\n';
- ret = len+1;
- } else {
- ret = PAGE_SIZE;
- }
+ if (device->module[0] == '\0')
+ return 0;
+
+ return sysfs_emit(buf, "%.*s\n", (int)sizeof(device->module), device->module);
}
- return ret;
+ return -ENOENT;
}
static ssize_t ddcci_attr_serial_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct ddcci_device *device = ddcci_verify_device(dev);
- ssize_t ret = -ENOENT;
if (likely(device != NULL))
- ret = scnprintf(buf, PAGE_SIZE, "%d\n", device->device_number);
+ return sysfs_emit(buf, "%d\n", device->device_number);
- return ret;
+ return -ENOENT;
}
static ssize_t ddcci_attr_modalias_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct ddcci_device *device = ddcci_verify_device(dev);
- ssize_t ret = -ENOENT;
char model[ARRAY_SIZE(device->model)];
char vendor[ARRAY_SIZE(device->model)];
char module[ARRAY_SIZE(device->model)];
@@ -895,16 +842,16 @@ static ssize_t ddcci_attr_modalias_show(struct device *dev,
ddcci_modalias_clean(vendor, sizeof(vendor), '_');
ddcci_modalias_clean(module, sizeof(module), '_');
- ret = scnprintf(buf, PAGE_SIZE, "%s%s-%s-%s-%s-%s\n",
+ return sysfs_emit(buf, "%s%.*s-%.*s-%.*s-%.*s-%.*s\n",
DDCCI_MODULE_PREFIX,
- device->prot,
- device->type,
- model,
- vendor,
- module
+ (int)sizeof(device->prot), device->prot,
+ (int)sizeof(device->type), device->type,
+ (int)sizeof(model), model,
+ (int)sizeof(vendor), vendor,
+ (int)sizeof(module), module
);
}
- return ret;
+ return -ENOENT;
}
static DEVICE_ATTR(capabilities, S_IRUGO, ddcci_attr_capabilities_show, NULL);
@@ -945,33 +892,33 @@ static int ddcci_device_uevent(CSTRUCT device *dev, struct kobj_uevent_env *env)
ddcci_modalias_clean(vendor, sizeof(vendor), '_');
ddcci_modalias_clean(module, sizeof(module), '_');
- if (add_uevent_var(env, "MODALIAS=%s%s-%s-%s-%s-%s",
+ if (add_uevent_var(env, "MODALIAS=%s%.*s-%.*s-%.*s-%.*s-%.*s",
DDCCI_MODULE_PREFIX,
- device->prot,
- device->type,
- model,
- vendor,
- module
+ (int)sizeof(device->prot), device->prot,
+ (int)sizeof(device->type), device->type,
+ (int)sizeof(model), model,
+ (int)sizeof(vendor), vendor,
+ (int)sizeof(module), module
))
return -ENOMEM;
if (device->prot[0])
- if (add_uevent_var(env, "DDCCI_PROT=%s", device->prot))
+ if (add_uevent_var(env, "DDCCI_PROT=%.*s", (int)sizeof(device->prot), device->prot))
return -ENOMEM;
if (device->type[0])
- if (add_uevent_var(env, "DDCCI_TYPE=%s", device->type))
+ if (add_uevent_var(env, "DDCCI_TYPE=%.*s", (int)sizeof(device->type), device->type))
return -ENOMEM;
if (device->model[0])
- if (add_uevent_var(env, "DDCCI_MODEL=%s", device->model))
+ if (add_uevent_var(env, "DDCCI_MODEL=%.*s", (int)sizeof(device->model), device->model))
return -ENOMEM;
if (device->vendor[0]) {
- if (add_uevent_var(env, "DDCCI_VENDOR=%s", device->vendor))
+ if (add_uevent_var(env, "DDCCI_VENDOR=%.*s", (int)sizeof(device->vendor), device->vendor))
return -ENOMEM;
- if (add_uevent_var(env, "DDCCI_MODULE=%s", device->module))
+ if (add_uevent_var(env, "DDCCI_MODULE=%.*s", (int)sizeof(device->module), device->module))
return -ENOMEM;
if (add_uevent_var(env, "DDCCI_UNIQ=%d", device->device_number))
--
2.54.0
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