usermodehelper: don't use CLONE_VFORK for ____call_usermodehelper()

After "kernel/kmod: fix use-after-free of the sub_infostructure"
CLONE_VFORK in __call_usermodehelper() buys nothing, we rely on on
umh_complete() in ____call_usermodehelper() anyway.

Remove it.  This also eliminates the unnecessary sleep/wakeup in the
likely case, and this allows the next change.

While at it, kill the "int wait" locals in ____call_usermodehelper() and
__call_usermodehelper(), they can safely use sub_info->wait.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: 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, 3 insertions, 9 deletions

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 80f7a6d00519..4621771b43b9 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -223,7 +223,6 @@ static void umh_complete(struct subprocess_info *sub_info)
 static int ____call_usermodehelper(void *data)
 {
         struct subprocess_info *sub_info = data;
-        int wait = sub_info->wait & ~UMH_KILLABLE;
         struct cred *new;
         int retval;
 
@@ -267,7 +266,7 @@ static int ____call_usermodehelper(void *data)
 out:
         sub_info->retval = retval;
         /* wait_for_helper() will call umh_complete if UHM_WAIT_PROC. */
-        if (wait != UMH_WAIT_PROC)
+        if (!(sub_info->wait & UMH_WAIT_PROC))
                 umh_complete(sub_info);
         if (!retval)
                 return 0;
@@ -323,18 +322,13 @@ static void __call_usermodehelper(struct work_struct *work)
 {
         struct subprocess_info *sub_info =
                 container_of(work, struct subprocess_info, work);
-        int wait = sub_info->wait & ~UMH_KILLABLE;
         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)
+        if (sub_info->wait & UMH_WAIT_PROC)
                 pid = kernel_thread(wait_for_helper, sub_info,
                                     CLONE_FS | CLONE_FILES | SIGCHLD);
         else {
-                pid = kernel_thread(call_helper, sub_info,
-                                    CLONE_VFORK | SIGCHLD);
+                pid = kernel_thread(call_helper, sub_info, SIGCHLD);
                 /* Worker thread stopped blocking khelper thread. */
                 kmod_thread_locker = NULL;
         }