[PATCH] usermodehelper: kill the sub_info->path[0] check

[Oleg Nesterov <oleg@redhat.com>]

call_usermodehelper_exec() does nothing but returns success if
path[0] == 0. The only user which needs this strange feature is
request_module(), it can check modprobe_path[0] itself like other
users do if they want to detect the "disabled by admin" case.

Kill it. Not only it looks strange, it can confuse other callers.
And this allows us to revert 264b83c0 "usermodehelper: check
subprocess_info->path != NULL", do_execve(NULL) is safe.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/kmod.c |   11 +++--------
 1 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 8241906..fb32636 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -147,6 +147,9 @@ int __request_module(bool wait, const char *fmt, ...)
 	 */
 	WARN_ON_ONCE(wait && current_is_async());
 
+	if (!modprobe_path[0])
+		return 0;
+
 	va_start(args, fmt);
 	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
 	va_end(args);
@@ -569,14 +572,6 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 	int retval = 0;
 
 	helper_lock();
-	if (!sub_info->path) {
-		retval = -EINVAL;
-		goto out;
-	}
-
-	if (sub_info->path[0] == '\0')
-		goto out;
-
 	if (!khelper_wq || usermodehelper_disabled) {
 		retval = -EBUSY;
 		goto out;
-- 
1.5.5.1