Patch "x86/pgtable: Don't set huge PUD/PMD on non-leaf entries" has been added to the 4.16-stable tree

Commit Message

Greg Kroah-Hartman May 27, 2018, 2:33 p.m. UTC

This is a note to let you know that I've just added the patch titled

    x86/pgtable: Don't set huge PUD/PMD on non-leaf entries

to the 4.16-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-pgtable-don-t-set-huge-pud-pmd-on-non-leaf-entries.patch
and it can be found in the queue-4.16 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <[e-mail]> know about it.


From foo@baz Sun May 27 16:10:02 CEST 2018
From: Joerg Roedel <[e-mail]>
Date: Wed, 11 Apr 2018 17:24:38 +0200
Subject: x86/pgtable: Don't set huge PUD/PMD on non-leaf entries

From: Joerg Roedel <[e-mail]>

[ Upstream commit e3e288121408c3abeed5af60b87b95c847143845 ]

The pmd_set_huge() and pud_set_huge() functions are used from
the generic ioremap() code to establish large mappings where this
is possible.

But the generic ioremap() code does not check whether the
PMD/PUD entries are already populated with a non-leaf entry,
so that any page-table pages these entries point to will be
lost.

Further, on x86-32 with SHARED_KERNEL_PMD=0, this causes a
BUG_ON() in vmalloc_sync_one() when PMD entries are synced
from swapper_pg_dir to the current page-table. This happens
because the PMD entry from swapper_pg_dir was promoted to a
huge-page entry while the current PGD still contains the
non-leaf entry. Because both entries are present and point
to a different page, the BUG_ON() triggers.

This was actually triggered with pti-x32 enabled in a KVM
virtual machine by the graphics driver.

A real and better fix for that would be to improve the
page-table handling in the generic ioremap() code. But that is
out-of-scope for this patch-set and left for later work.

Reported-by: David H. Gutteridge <[e-mail]>
Signed-off-by: Joerg Roedel <[e-mail]>
Reviewed-by: Thomas Gleixner <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Boris Ostrovsky <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Brian Gerst <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: David Laight <[e-mail]>
Cc: Denys Vlasenko <[e-mail]>
Cc: Eduardo Valentin <[e-mail]>
Cc: Greg KH <[e-mail]>
Cc: Jiri Kosina <[e-mail]>
Cc: Josh Poimboeuf <[e-mail]>
Cc: Juergen Gross <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Pavel Machek <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Waiman Long <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>
Signed-off-by: Sasha Levin <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>
---
 arch/x86/mm/pgtable.c |    9 +++++++++
 1 file changed, 9 insertions(+)



Patches currently in stable-queue which might be from [e-mail] are

queue-4.16/x86-apic-set-up-through-local-apic-mode-on-the-boot-cpu-if-noapic-specified.patch
queue-4.16/x86-pgtable-don-t-set-huge-pud-pmd-on-non-leaf-entries.patch

Patch

--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -1,6 +1,7 @@ 
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/mm.h>
 #include <linux/gfp.h>
+#include <linux/hugetlb.h>
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
 #include <asm/tlb.h>
@@ -636,6 +637,10 @@  int pud_set_huge(pud_t *pud, phys_addr_t
 	    (mtrr != MTRR_TYPE_WRBACK))
 		return 0;
 
+	/* Bail out if we are we on a populated non-leaf entry: */
+	if (pud_present(*pud) && !pud_huge(*pud))
+		return 0;
+
 	prot = pgprot_4k_2_large(prot);
 
 	set_pte((pte_t *)pud, pfn_pte(
@@ -664,6 +669,10 @@  int pmd_set_huge(pmd_t *pmd, phys_addr_t
 		return 0;
 	}
 
+	/* Bail out if we are we on a populated non-leaf entry: */
+	if (pmd_present(*pmd) && !pmd_huge(*pmd))
+		return 0;
+
 	prot = pgprot_4k_2_large(prot);
 
 	set_pte((pte_t *)pmd, pfn_pte(