Commit dedca635 authored Jun 13, 2019 by Potyra, Stefan Committed by Linus Torvalds Jun 13, 2019

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: b0f205c2 ("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>

parent c04e32e9

mm/mlock.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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())

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