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@er01809n.ebgroup.elektrobit.com
Fixes: b0f205c2a308 ("mm: mlock: add mlock flags to enable VM_LOCKONFAULT usage")
Signed-off-by: Stefan Potyra <Stefan.Potyra@elektrobit.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/mlock.c b/mm/mlock.c
index 080f3b3..cef65bf 100644
--- a/mm/mlock.c
+++ b/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())