From 10d22b31e3945329c46e2faae4d25924a180b144 Mon Sep 17 00:00:00 2001 From: hongfeng Date: Wed, 26 Sep 2012 11:34:13 +1000 Subject: [PATCH] poweroff: fix bug in orderly_poweroff() orderly_poweroff is trying to poweroff platform in two steps: step 1: Call user space application to poweroff step 2: If user space poweroff fail, then do a force power off if force param is set. The bug here is, step 1 is always successful with param UMH_NO_WAIT, which obey the design goal of orderly_poweroff. We have two choices here: UMH_WAIT_EXEC which means wait for the exec, but not the process; UMH_WAIT_PROC which means wait for the process to complete. we need to trade off the two choices: If using UMH_WAIT_EXEC, there is potential issue comments by Serge E. Hallyn: The exec will have started, but may for whatever (very unlikely) reason fail. If using UMH_WAIT_PROC, there is potential issue comments by Eric W. Biederman: If the caller is not running in a kernel thread then we can easily get into a case where the user space caller will block waiting for us when we are waiting for the user space caller. Thanks for their excellent ideas, based on the above discussion, we finally choose UMH_WAIT_EXEC, which is much more safe, if the user application really fails, we just complain the application itself, it seems a better choice here. Signed-off-by: Feng Hong Acked-by: Kees Cook Acked-by: Serge Hallyn Cc: "Eric W. Biederman" Acked-by: "Rafael J. Wysocki" Signed-off-by: Andrew Morton --- kernel/sys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sys.c b/kernel/sys.c index e2d12b352d92..de4af92c0934 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2205,7 +2205,7 @@ static int __orderly_poweroff(void) return -ENOMEM; } - ret = call_usermodehelper_fns(argv[0], argv, envp, UMH_NO_WAIT, + ret = call_usermodehelper_fns(argv[0], argv, envp, UMH_WAIT_EXEC, NULL, argv_cleanup, NULL); if (ret == -ENOMEM) argv_free(argv); -- 2.39.5