[PATCH 3.16 129/131] HID: debug: check length before copy_to_user()

[Ben Hutchings]

3.16.59-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Rosenberg <dro...@google.com>

commit 717adfdaf14704fd3ec7fa2c04520c0723247eac upstream.

If our length is greater than the size of the buffer, we
overflow the buffer

Signed-off-by: Daniel Rosenberg <dro...@google.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoi...@redhat.com>
Signed-off-by: Jiri Kosina <jkos...@suse.cz>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 drivers/hid/hid-debug.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -1150,6 +1150,8 @@ copy_rest:
                        goto out;
                if (list->tail > list->head) {
                        len = list->tail - list->head;
+                       if (len > count)
+                               len = count;
 
                        if (copy_to_user(buffer + ret, 
&list->hid_debug_buf[list->head], len)) {
                                ret = -EFAULT;
@@ -1159,6 +1161,8 @@ copy_rest:
                        list->head += len;
                } else {
                        len = HID_DEBUG_BUFSIZE - list->head;
+                       if (len > count)
+                               len = count;
 
                        if (copy_to_user(buffer, 
&list->hid_debug_buf[list->head], len)) {
                                ret = -EFAULT;
@@ -1166,7 +1170,9 @@ copy_rest:
                        }
                        list->head = 0;
                        ret += len;
-                       goto copy_rest;
+                       count -= len;
+                       if (count > 0)
+                               goto copy_rest;
                }
 
        }