diff options
| -rw-r--r-- | Documentation/acpi/method-customizing.txt | 5 | ||||
| -rw-r--r-- | drivers/acpi/Kconfig | 15 | ||||
| -rw-r--r-- | drivers/acpi/Makefile | 1 | ||||
| -rw-r--r-- | drivers/acpi/custom_method.c | 100 | ||||
| -rw-r--r-- | drivers/acpi/debugfs.c | 80 |
5 files changed, 122 insertions, 79 deletions
diff --git a/Documentation/acpi/method-customizing.txt b/Documentation/acpi/method-customizing.txt index 3e1d25aee3fb..5f55373dd53b 100644 --- a/Documentation/acpi/method-customizing.txt +++ b/Documentation/acpi/method-customizing.txt @@ -66,3 +66,8 @@ Note: We can use a kernel with multiple custom ACPI method running, But each individual write to debugfs can implement a SINGLE method override. i.e. if we want to insert/override multiple ACPI methods, we need to redo step c) ~ g) for multiple times. + +Note: Be aware that root can mis-use this driver to modify arbitrary + memory and gain additional rights, if root's privileges got + restricted (for example if root is not allowed to load additional + modules after boot). diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig index 3a17ca5fff6f..d918e130bef3 100644 --- a/drivers/acpi/Kconfig +++ b/drivers/acpi/Kconfig @@ -380,6 +380,21 @@ config ACPI_HED which is used to report some hardware errors notified via SCI, mainly the corrected errors. +config ACPI_CUSTOM_METHOD + tristate "Allow ACPI methods to be inserted/replaced at run time" + depends on DEBUG_FS + default n + help + This debug facility allows ACPI AML methods to me inserted and/or + replaced without rebooting the system. For details refer to: + Documentation/acpi/method-customizing.txt. + + NOTE: This option is security sensitive, because it allows arbitrary + kernel memory to be written to by root (uid=0) users, allowing them + to bypass certain security measures (e.g. if root is not allowed to + load additional kernel modules after boot, this feature may be used + to override that restriction). + source "drivers/acpi/apei/Kconfig" endif # ACPI diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile index d113fa5100b2..cba0b2334b9b 100644 --- a/drivers/acpi/Makefile +++ b/drivers/acpi/Makefile @@ -62,6 +62,7 @@ obj-$(CONFIG_ACPI_SBS) += sbs.o obj-$(CONFIG_ACPI_POWER_METER) += power_meter.o obj-$(CONFIG_ACPI_HED) += hed.o obj-$(CONFIG_ACPI_EC_DEBUGFS) += ec_sys.o +obj-$(CONFIG_ACPI_CUSTOM_METHOD)+= custom_method.o # processor has its own "processor." module_param namespace processor-y := processor_driver.o processor_throttling.o diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c new file mode 100644 index 000000000000..5d42c2414ae5 --- /dev/null +++ b/drivers/acpi/custom_method.c @@ -0,0 +1,100 @@ +/* + * debugfs.c - ACPI debugfs interface to userspace. + */ + +#include <linux/init.h> +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/uaccess.h> +#include <linux/debugfs.h> +#include <acpi/acpi_drivers.h> + +#include "internal.h" + +#define _COMPONENT ACPI_SYSTEM_COMPONENT +ACPI_MODULE_NAME("custom_method"); +MODULE_LICENSE("GPL"); + +static struct dentry *cm_dentry; + +/* /sys/kernel/debug/acpi/custom_method */ + +static ssize_t cm_write(struct file *file, const char __user * user_buf, + size_t count, loff_t *ppos) +{ + static char *buf; + static u32 max_size; + static u32 uncopied_bytes; + + struct acpi_table_header table; + acpi_status status; + + if (!(*ppos)) { + /* parse the table header to get the table length */ + if (count <= sizeof(struct acpi_table_header)) + return -EINVAL; + if (copy_from_user(&table, user_buf, + sizeof(struct acpi_table_header))) + return -EFAULT; + uncopied_bytes = max_size = table.length; + buf = kzalloc(max_size, GFP_KERNEL); + if (!buf) + return -ENOMEM; + } + + if (buf == NULL) + return -EINVAL; + + if ((*ppos > max_size) || + (*ppos + count > max_size) || + (*ppos + count < count) || + (count > uncopied_bytes)) + return -EINVAL; + + if (copy_from_user(buf + (*ppos), user_buf, count)) { + kfree(buf); + buf = NULL; + return -EFAULT; + } + + uncopied_bytes -= count; + *ppos += count; + + if (!uncopied_bytes) { + status = acpi_install_method(buf); + kfree(buf); + buf = NULL; + if (ACPI_FAILURE(status)) + return -EINVAL; + add_taint(TAINT_OVERRIDDEN_ACPI_TABLE); + } + + return count; +} + +static const struct file_operations cm_fops = { + .write = cm_write, + .llseek = default_llseek, +}; + +static int __init acpi_custom_method_init(void) +{ + if (acpi_debugfs_dir == NULL) + return -ENOENT; + + cm_dentry = debugfs_create_file("custom_method", S_IWUSR, + acpi_debugfs_dir, NULL, &cm_fops); + if (cm_dentry == NULL) + return -ENODEV; + + return 0; +} + +static void __exit acpi_custom_method_exit(void) +{ + if (cm_dentry) + debugfs_remove(cm_dentry); + } + +module_init(acpi_custom_method_init); +module_exit(acpi_custom_method_exit); diff --git a/drivers/acpi/debugfs.c b/drivers/acpi/debugfs.c index e7abc6e3bba0..182a9fc36355 100644 --- a/drivers/acpi/debugfs.c +++ b/drivers/acpi/debugfs.c @@ -3,9 +3,6 @@ */ #include <linux/init.h> -#include <linux/module.h> -#include <linux/kernel.h> -#include <linux/uaccess.h> #include <linux/debugfs.h> #include <acpi/acpi_drivers.h> @@ -13,84 +10,9 @@ ACPI_MODULE_NAME("debugfs"); struct dentry *acpi_debugfs_dir; -static struct dentry *cm_dentry; - -/* /sys/kernel/debug/acpi/custom_method */ - -static ssize_t cm_write(struct file *file, const char __user * user_buf, - size_t count, loff_t *ppos) -{ - static char *buf; - static u32 max_size; - static u32 uncopied_bytes; - - struct acpi_table_header table; - acpi_status status; - - if (!(*ppos)) { - /* parse the table header to get the table length */ - if (count <= sizeof(struct acpi_table_header)) - return -EINVAL; - if (copy_from_user(&table, user_buf, - sizeof(struct acpi_table_header))) - return -EFAULT; - uncopied_bytes = max_size = table.length; - buf = kzalloc(max_size, GFP_KERNEL); - if (!buf) - return -ENOMEM; - } - - if (buf == NULL) - return -EINVAL; - - if ((*ppos > max_size) || - (*ppos + count > max_size) || - (*ppos + count < count) || - (count > uncopied_bytes)) - return -EINVAL; - - if (copy_from_user(buf + (*ppos), user_buf, count)) { - kfree(buf); - buf = NULL; - return -EFAULT; - } - - uncopied_bytes -= count; - *ppos += count; - - if (!uncopied_bytes) { - status = acpi_install_method(buf); - kfree(buf); - buf = NULL; - if (ACPI_FAILURE(status)) - return -EINVAL; - add_taint(TAINT_OVERRIDDEN_ACPI_TABLE); - } - - return count; -} - -static const struct file_operations cm_fops = { - .write = cm_write, - .llseek = default_llseek, -}; - -static int __init acpi_custom_method_init(void) -{ - if (!acpi_debugfs_dir) - return -ENOENT; - - cm_dentry = debugfs_create_file("custom_method", S_IWUSR, - acpi_debugfs_dir, NULL, &cm_fops); - if (!cm_dentry) - return -ENODEV; - - return 0; -} +EXPORT_SYMBOL_GPL(acpi_debugfs_dir); void __init acpi_debugfs_init(void) { acpi_debugfs_dir = debugfs_create_dir("acpi", NULL); - - acpi_custom_method_init(); } |