ACPI: Split out custom_method functionality into an own driver
With /sys/kernel/debug/acpi/custom_method root can write
to arbitrary memory and increase his priveleges, even if
these are restricted.
-> Make this an own debug .config option and warn about the
security issue in the config description.
-> Still keep acpi/debugfs.c which now only creates an empty
/sys/kernel/debug/acpi directory. There might be other
users of it later.
Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: rui.zhang@intel.com
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
new file mode 100644
index 0000000..5d42c24
--- /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);