From f3093590ab485c98943434812325fc7d87bf83e9 Mon Sep 17 00:00:00 2001
From: David Herrmann <dh.herrmann@gmail.com>
Date: Thu, 15 Jan 2015 12:38:57 +0100
Subject: [PATCH] udev: fix NULL-ptr deref

Make sure we properly validate the return value of
udev_device_get_sysattr_value(). It might be NULL for several reasons.

(cherry picked from commit 975a900782528b57deafadc10457c7ffab0b9791)
---
 src/udev/udev-builtin-input_id.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/udev/udev-builtin-input_id.c b/src/udev/udev-builtin-input_id.c
index 1a1121ef94..8acd74200a 100644
--- a/src/udev/udev-builtin-input_id.c
+++ b/src/udev/udev-builtin-input_id.c
@@ -4,6 +4,7 @@
  * Copyright (C) 2009 Martin Pitt <martin.pitt@ubuntu.com>
  * Portions Copyright (C) 2004 David Zeuthen, <david@fubar.dk>
  * Copyright (C) 2011 Kay Sievers <kay@vrfy.org>
+ * Copyright (C) 2014 David Herrmann <dh.herrmann@gmail.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -48,12 +49,17 @@ static void get_cap_mask(struct udev_device *dev,
                          struct udev_device *pdev, const char* attr,
                          unsigned long *bitmask, size_t bitmask_size,
                          bool test) {
+        const char *v;
         char text[4096];
         unsigned i;
         char* word;
         unsigned long val;
 
-        snprintf(text, sizeof(text), "%s", udev_device_get_sysattr_value(pdev, attr));
+        v = udev_device_get_sysattr_value(pdev, attr);
+        if (!v)
+                v = "";
+
+        snprintf(text, sizeof(text), "%s", v);
         log_debug("%s raw kernel attribute: %s", attr, text);
 
         memzero(bitmask, bitmask_size);