• hongfeng's avatar
    poweroff: fix bug in orderly_poweroff() · 6c0c0d4d
    hongfeng authored
    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: default avatarFeng Hong <hongfeng@marvell.com>
    Acked-by: default avatarKees Cook <keescook@chromium.org>
    Acked-by: default avatarSerge Hallyn <serge.hallyn@canonical.com>
    Cc: "Eric W. Biederman" <ebiederm@xmission.com>
    Acked-by: default avatar"Rafael J. Wysocki" <rjw@sisk.pl>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    6c0c0d4d
sys.c 52.1 KB