call_usermodehelper: simplify/fix UMH_NO_WAIT case

__call_usermodehelper(UMH_NO_WAIT) has 2 problems:

	- if kernel_thread() fails, call_usermodehelper_freeinfo()
	  is not called.

	- for unknown reason UMH_NO_WAIT has UMH_WAIT_PROC logic,
	  we spawn yet another thread which waits until the user
	  mode application exits.

Change the UMH_NO_WAIT code to use ____call_usermodehelper() instead of
wait_for_helper(), and do call_usermodehelper_freeinfo() unconditionally.
We can rely on CLONE_VFORK, do_fork(CLONE_VFORK) until the child exits or
execs.

With or without this patch UMH_NO_WAIT does not report the error if
kernel_thread() fails, this is correct since the caller doesn't wait for
result.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 6 deletions

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 48daed4c51ba..ad9f2edebd67 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -205,10 +205,7 @@ static int wait_for_helper(void *data)
                         sub_info->retval = ret;
         }
 
-        if (sub_info->wait == UMH_NO_WAIT)
-                call_usermodehelper_freeinfo(sub_info);
-        else
-                complete(sub_info->complete);
+        complete(sub_info->complete);
         return 0;
 }
 
@@ -217,13 +214,13 @@ static void __call_usermodehelper(struct work_struct *work)
 {
         struct subprocess_info *sub_info =
                 container_of(work, struct subprocess_info, work);
-        pid_t pid;
         enum umh_wait wait = sub_info->wait;
+        pid_t pid;
 
         /* CLONE_VFORK: wait until the usermode helper has execve'd
          * successfully We need the data structures to stay around
          * until that is done.  */
-        if (wait == UMH_WAIT_PROC || wait == UMH_NO_WAIT)
+        if (wait == UMH_WAIT_PROC)
                 pid = kernel_thread(wait_for_helper, sub_info,
                                     CLONE_FS | CLONE_FILES | SIGCHLD);
         else
@@ -232,6 +229,7 @@ static void __call_usermodehelper(struct work_struct *work)
 
         switch (wait) {
         case UMH_NO_WAIT:
+                call_usermodehelper_freeinfo(sub_info);
                 break;
 
         case UMH_WAIT_PROC: