2 files changed, 27 insertions, 2 deletions

diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index 722f477c4ef7..1b5985855ffc 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -54,6 +54,8 @@ enum umh_wait {
         UMH_WAIT_PROC = 1,      /* wait for the process to complete */
 };
 
+#define UMH_KILLABLE    4       /* wait for EXEC/PROC killable */
+
 struct subprocess_info {
         struct work_struct work;
         struct completion *complete;
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 8ea25944ce33..f92f917c450c 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -201,7 +201,15 @@ EXPORT_SYMBOL(call_usermodehelper_freeinfo);
 
 static void umh_complete(struct subprocess_info *sub_info)
 {
-        complete(sub_info->complete);
+        struct completion *comp = xchg(&sub_info->complete, NULL);
+        /*
+         * See call_usermodehelper_exec(). If xchg() returns NULL
+         * we own sub_info, the UMH_KILLABLE caller has gone away.
+         */
+        if (comp)
+                complete(comp);
+        else
+                call_usermodehelper_freeinfo(sub_info);
 }
 
 /* Keventd can't block, but this (a child) can. */
@@ -252,6 +260,9 @@ static void __call_usermodehelper(struct work_struct *work)
         enum umh_wait wait = sub_info->wait;
         pid_t pid;
 
+        if (wait != UMH_NO_WAIT)
+                wait &= ~UMH_KILLABLE;
+
         /* CLONE_VFORK: wait until the usermode helper has execve'd
          * successfully We need the data structures to stay around
          * until that is done.  */
@@ -461,9 +472,21 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info,
         queue_work(khelper_wq, &sub_info->work);
         if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
                 goto unlock;
+
+        if (wait & UMH_KILLABLE) {
+                retval = wait_for_completion_killable(&done);
+                if (!retval)
+                        goto wait_done;
+
+                /* umh_complete() will see NULL and free sub_info */
+                if (xchg(&sub_info->complete, NULL))
+                        goto unlock;
+                /* fallthrough, umh_complete() was already called */
+        }
+
         wait_for_completion(&done);
+wait_done:
         retval = sub_info->retval;
-
 out:
         call_usermodehelper_freeinfo(sub_info);
 unlock: