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From:   Sasha Levin <Alexander.Levin@microsoft.com>
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CC:     Joerg Roedel <jroedel@suse.de>,
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        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.18 87/88] x86/mm/pti: Add an overflow check to
 pti_clone_pmds()
Thread-Topic: [PATCH AUTOSEL 4.18 87/88] x86/mm/pti: Add an overflow check to
 pti_clone_pmds()
Thread-Index: AQHURkLfBdAoKRBJBE+KJ3vVDo65pA==
Date:   Fri, 7 Sep 2018 00:36:53 +0000
Message-ID: <20180907003547.57567-87-alexander.levin@microsoft.com>
References: <20180907003547.57567-1-alexander.levin@microsoft.com>
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From: Joerg Roedel <jroedel@suse.de>

[ Upstream commit 935232ce28dfabff1171e5a7113b2d865fa9ee63 ]

The addr counter will overflow if the last PMD of the address space is
cloned, resulting in an endless loop.

Check for that and bail out of the loop when it happens.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Pavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-25-git-send-email-joro@8by=
tes.org
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 arch/x86/mm/pti.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index ffa2f0f67904..1d2106d83b4e 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -306,6 +306,10 @@ pti_clone_pmds(unsigned long start, unsigned long end,=
 pmdval_t clear)
 		p4d_t *p4d;
 		pud_t *pud;
=20
+		/* Overflow check */
+		if (addr < start)
+			break;
+
 		pgd =3D pgd_offset_k(addr);
 		if (WARN_ON(pgd_none(*pgd)))
 			return;
--=20
2.17.1