HID: debug: check length before copy_to_user()

commit 717adfdaf14704fd3ec7fa2c04520c0723247eac upstream.

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

Cc: stable@vger.kernel.org
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index 4f4e7a08a07be5c0a37c129905e89d4e03aa10e0..4db8e140f7096d3764aa3cc5ea1a6f68b9b7268c 100644 (file)
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -1154,6 +1154,8 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
                        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;
@@ -1163,6 +1165,8 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
                        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;
@@ -1170,7 +1174,9 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
                        }
                        list->head = 0;
                        ret += len;
-                       goto copy_rest;
+                       count -= len;
+                       if (count > 0)
+                               goto copy_rest;
                }
 
        }