Merge tag 'driver-core-4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core updates from Greg KH:
 "Here is the "small" driver core patches for 4.11-rc1.

  Not much here, some firmware documentation and self-test updates, a
  debugfs code formatting issue, and a new feature for call_usermodehelper
  to make it more robust on systems that want to lock it down in a more
  secure way.

  All of these have been linux-next for a while now with no reported
  issues"

* tag 'driver-core-4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  kernfs: handle null pointers while printing node name and path
  Introduce STATIC_USERMODEHELPER to mediate call_usermodehelper()
  Make static usermode helper binaries constant
  kmod: make usermodehelper path a const string
  firmware: revamp firmware documentation
  selftests: firmware: send expected errors to /dev/null
  selftests: firmware: only modprobe if driver is missing
  platform: Print the resource range if device failed to claim
  kref: prefer atomic_inc_not_zero to atomic_add_unless
  debugfs: improve formatting of debugfs_real_fops()

1 files changed, 16 insertions, 2 deletions

diff --git a/kernel/kmod.c b/kernel/kmod.c
index d45c96073afb..0c407f905ca4 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -516,7 +516,7 @@ static void helper_unlock(void)
  * Function must be runnable in either a process context or the
  * context in which call_usermodehelper_exec is called.
  */
-struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
+struct subprocess_info *call_usermodehelper_setup(const char *path, char **argv,
 		char **envp, gfp_t gfp_mask,
 		int (*init)(struct subprocess_info *info, struct cred *new),
 		void (*cleanup)(struct subprocess_info *info),
@@ -528,7 +528,12 @@ struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
 		goto out;
 
 	INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
+
+#ifdef CONFIG_STATIC_USERMODEHELPER
+	sub_info->path = CONFIG_STATIC_USERMODEHELPER_PATH;
+#else
 	sub_info->path = path;
+#endif
 	sub_info->argv = argv;
 	sub_info->envp = envp;
 
@@ -566,6 +571,15 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 		retval = -EBUSY;
 		goto out;
 	}
+
+	/*
+	 * If there is no binary for us to call, then just return and get out of
+	 * here.  This allows us to set STATIC_USERMODEHELPER_PATH to "" and
+	 * disable all call_usermodehelper() calls.
+	 */
+	if (strlen(sub_info->path) == 0)
+		goto out;
+
 	/*
 	 * Set the completion pointer only if there is a waiter.
 	 * This makes it possible to use umh_complete to free
@@ -613,7 +627,7 @@ EXPORT_SYMBOL(call_usermodehelper_exec);
  * This function is the equivalent to use call_usermodehelper_setup() and
  * call_usermodehelper_exec().
  */
-int call_usermodehelper(char *path, char **argv, char **envp, int wait)
+int call_usermodehelper(const char *path, char **argv, char **envp, int wait)
 {
 	struct subprocess_info *info;
 	gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;