1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/acpi/proc.c b/drivers/acpi/proc.c
index d0d550d22a6d..d0d25e2e1ced 100644
--- a/drivers/acpi/proc.c
+++ b/drivers/acpi/proc.c
@@ -393,11 +393,13 @@ acpi_system_write_wakeup_device(struct file *file,
         struct list_head *node, *next;
         char strbuf[5];
         char str[5] = "";
-        int len = count;
+        unsigned int len = count;
         struct acpi_device *found_dev = NULL;
 
         if (len > 4)
                 len = 4;
+        if (len < 0)
+                return -EFAULT;
 
         if (copy_from_user(strbuf, buffer, len))
                 return -EFAULT;