1 files changed, 14 insertions, 6 deletions

diff --git a/drivers/acpi/debugfs.c b/drivers/acpi/debugfs.c
index 5df67f1d6c61..384f7abcff77 100644
--- a/drivers/acpi/debugfs.c
+++ b/drivers/acpi/debugfs.c
@@ -26,7 +26,9 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
                         size_t count, loff_t *ppos)
 {
         static char *buf;
-        static int uncopied_bytes;
+        static u32 max_size;
+        static u32 uncopied_bytes;
+
         struct acpi_table_header table;
         acpi_status status;
 
@@ -37,19 +39,24 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
                 if (copy_from_user(&table, user_buf,
                                    sizeof(struct acpi_table_header)))
                         return -EFAULT;
-                uncopied_bytes = table.length;
-                buf = kzalloc(uncopied_bytes, GFP_KERNEL);
+                uncopied_bytes = max_size = table.length;
+                buf = kzalloc(max_size, GFP_KERNEL);
                 if (!buf)
                         return -ENOMEM;
         }
 
-        if (uncopied_bytes < count) {
-                kfree(buf);
+        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;
         }
 
@@ -59,6 +66,7 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
         if (!uncopied_bytes) {
                 status = acpi_install_method(buf);
                 kfree(buf);
+                buf = NULL;
                 if (ACPI_FAILURE(status))
                         return -EINVAL;
                 add_taint(TAINT_OVERRIDDEN_ACPI_TABLE);