ACPI: avoid empty file name in sysfs

Since commit bc45b1d39a925b56796bebf8a397a0491489d85c acpi tables are
allowed to have an empty signature and /sys/firmware/acpi/tables uses the
signature as filename.  Applications using naive recursion through /sys
loop forever.  A possible solution would be: (replacing the zero length
filename with the string "NULL")

http://bugzilla.kernel.org/show_bug.cgi?id=11539

Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 17 insertions, 8 deletions

diff --git a/drivers/acpi/system.c b/drivers/acpi/system.c
index 1d74171b7940..62ec75e79120 100644
--- a/drivers/acpi/system.c
+++ b/drivers/acpi/system.c
@@ -78,9 +78,15 @@ static ssize_t acpi_table_show(struct kobject *kobj,
             container_of(bin_attr, struct acpi_table_attr, attr);
         struct acpi_table_header *table_header = NULL;
         acpi_status status;
+        char name[ACPI_NAME_SIZE];
+
+        if (strncmp(table_attr->name, "NULL", 4))
+                memcpy(name, table_attr->name, ACPI_NAME_SIZE);
+        else
+                memcpy(name, "\0\0\0\0", 4);
 
         status =
-            acpi_get_table(table_attr->name, table_attr->instance,
+            acpi_get_table(name, table_attr->instance,
                            &table_header);
         if (ACPI_FAILURE(status))
                 return -ENODEV;
@@ -95,21 +101,24 @@ static void acpi_table_attr_init(struct acpi_table_attr *table_attr,
         struct acpi_table_header *header = NULL;
         struct acpi_table_attr *attr = NULL;
 
-        memcpy(table_attr->name, table_header->signature, ACPI_NAME_SIZE);
+        if (table_header->signature[0] != '\0')
+                memcpy(table_attr->name, table_header->signature,
+                        ACPI_NAME_SIZE);
+        else
+                memcpy(table_attr->name, "NULL", 4);
 
         list_for_each_entry(attr, &acpi_table_attr_list, node) {
-                if (!memcmp(table_header->signature, attr->name,
-                            ACPI_NAME_SIZE))
+                if (!memcmp(table_attr->name, attr->name, ACPI_NAME_SIZE))
                         if (table_attr->instance < attr->instance)
                                 table_attr->instance = attr->instance;
         }
         table_attr->instance++;
 
         if (table_attr->instance > 1 || (table_attr->instance == 1 &&
-                                         !acpi_get_table(table_header->
-                                                         signature, 2,
-                                                         &header)))
-                sprintf(table_attr->name + 4, "%d", table_attr->instance);
+                                        !acpi_get_table
+                                        (table_header->signature, 2, &header)))
+                sprintf(table_attr->name + ACPI_NAME_SIZE, "%d",
+                        table_attr->instance);
 
         table_attr->attr.size = 0;
         table_attr->attr.read = acpi_table_show;