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Subject[PATCH] mm: mlockall error for flag MCL_ONFAULT
Date
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.

Consequently, return the error EINVAL, if only MCL_ONFAULT
is passed. That way, applications will at least detect that
they are calling mlockall() incorrectly.

Fixes: b0f205c2a308 ("mm: mlock: add mlock flags to enable VM_LOCKONFAULT usage")
Signed-off-by: Stefan Potyra <Stefan.Potyra@elektrobit.com>
---
Sparse shows a warning for mlock.c, but it is not related to
this patch.

mm/mlock.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index e492a155c51a..03f39cbdd4c4 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())
--
2.20.1
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