From: "Potyra, Stefan" <Stefan.Potyra@xxxxxxxxxxxxxx> Subject: mm/mlock.c: mlockall error for flag MCL_ONFAULT If mlockall() is called with only MCL_ONFAULT as flag, it removes any previously applied lockings and does nothing else. This behavior is counter-intuitive and doesn't match the Linux man page. For mlockall(): EINVAL Unknown flags were specified or MCL_ONFAULT was specified without either MCL_FUTURE or MCL_CURRENT. Consequently, return the error EINVAL, if only MCL_ONFAULT is passed. That way, applications will at least detect that they are calling mlockall() incorrectly. Link: http://lkml.kernel.org/r/20190527075333.GA6339@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Fixes: b0f205c2a308 ("mm: mlock: add mlock flags to enable VM_LOCKONFAULT usage") Signed-off-by: Stefan Potyra <Stefan.Potyra@xxxxxxxxxxxxxx> Reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/mlock.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/mm/mlock.c~mm-mlockall-error-for-flag-mcl_onfault +++ a/mm/mlock.c @@ -797,7 +797,8 @@ SYSCALL_DEFINE1(mlockall, int, flags) unsigned long lock_limit; int ret; - if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT))) + if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) || + flags == MCL_ONFAULT) return -EINVAL; if (!can_do_mlock()) _
