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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Vasily Gorbik <gor@linux.ibm.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.18 023/136] s390/mm: correct allocate_pgste
 proc_handler callback
Thread-Topic: [PATCH AUTOSEL 4.18 023/136] s390/mm: correct allocate_pgste
 proc_handler callback
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Date:   Mon, 17 Sep 2018 03:00:25 +0000
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From: Vasily Gorbik <gor@linux.ibm.com>

[ Upstream commit 5bedf8aa03c28cb8dc98bdd32a41b66d8f7d3eaa ]

Since proc_dointvec does not perform value range control,
proc_dointvec_minmax should be used to limit value range, which is
clearly intended here, as the internal representation of the value:

unsigned int alloc_pgste:1;

In fact it currently works, since we have

      mm->context.alloc_pgste =3D page_table_allocate_pgste || ...

... since commit 23fefe119ceb5 ("s390/kvm: avoid global config of vm.alloc_=
pgste=3D1")

Before that it was

       mm->context.alloc_pgste =3D page_table_allocate_pgste;

which was broken. That was introduced with commit 0b46e0a3ec0d7 ("s390/kvm:
remove delayed reallocation of page tables for KVM").

Fixes: 0b46e0a3ec0d7 ("s390/kvm: remove delayed reallocation of page tables=
 for KVM")
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 arch/s390/mm/pgalloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c
index e3bd5627afef..76d89ee8b428 100644
--- a/arch/s390/mm/pgalloc.c
+++ b/arch/s390/mm/pgalloc.c
@@ -28,7 +28,7 @@ static struct ctl_table page_table_sysctl[] =3D {
 		.data		=3D &page_table_allocate_pgste,
 		.maxlen		=3D sizeof(int),
 		.mode		=3D S_IRUGO | S_IWUSR,
-		.proc_handler	=3D proc_dointvec,
+		.proc_handler	=3D proc_dointvec_minmax,
 		.extra1		=3D &page_table_allocate_pgste_min,
 		.extra2		=3D &page_table_allocate_pgste_max,
 	},
--=20
2.17.1