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From:   Joerg Roedel <joro@8bytes.org>
To:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>
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        Linus Torvalds <torvalds@linux-foundation.org>,
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        Waiman Long <llong@redhat.com>, Pavel Machek <pavel@ucw.cz>,
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Subject: [PATCH 22/31] x86/mm/pti: Add an overflow check to pti_clone_pmds()
Date:   Fri,  9 Feb 2018 10:25:31 +0100
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From: Joerg Roedel <jroedel@suse.de>

The addr counter will overflow if we clone the last PMD of
the address space, 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>
---
 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 ce38f16..7f5e698 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -282,6 +282,10 @@ pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear)
 		p4d_t *p4d;
 		pud_t *pud;
 
+		/* Overflow check */
+		if (addr < start)
+			break;
+
 		pgd = pgd_offset_k(addr);
 		if (WARN_ON(pgd_none(*pgd)))
 			return;
-- 
2.7.4