linux-kernel - [tip:x86/pti] x86/kexec: Allocate 8k PGDs for PTI

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Message-ID: <tip-ca38dc8f2724d101038b1205122c93a1c7f38f11@git.kernel.org>
Date:   Mon, 30 Jul 2018 04:58:57 -0700
From:   tip-bot for Joerg Roedel <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     aarcange@...hat.com, boris.ostrovsky@...cle.com, llong@...hat.com,
        dave.hansen@...el.com, namhyung@...nel.org,
        torvalds@...ux-foundation.org, eduval@...zon.com, bp@...en8.de,
        dhgutteridge@...patico.ca, gregkh@...uxfoundation.org,
        acme@...nel.org, jolsa@...hat.com, jgross@...e.com,
        tglx@...utronix.de, mingo@...nel.org,
        alexander.shishkin@...ux.intel.com, dvlasenk@...hat.com,
        jroedel@...e.de, David.Laight@...lab.com, hpa@...or.com,
        will.deacon@....com, jpoimboe@...hat.com, luto@...nel.org,
        brgerst@...il.com, linux-kernel@...r.kernel.org, jkosina@...e.cz,
        pavel@....cz, peterz@...radead.org
Subject: [tip:x86/pti] x86/kexec: Allocate 8k PGDs for PTI

Commit-ID:  ca38dc8f2724d101038b1205122c93a1c7f38f11
Gitweb:     https://git.kernel.org/tip/ca38dc8f2724d101038b1205122c93a1c7f38f11
Author:     Joerg Roedel <jroedel@...e.de>
AuthorDate: Wed, 25 Jul 2018 17:48:03 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Mon, 30 Jul 2018 13:53:48 +0200

x86/kexec: Allocate 8k PGDs for PTI

Fuzzing the PTI-x86-32 code with trinity showed unhandled
kernel paging request oops-messages that looked a lot like
silent data corruption.

Lot's of debugging and testing lead to the kexec-32bit code,
which is still allocating 4k PGDs when PTI is enabled. But
since it uses native_set_pud() to build the page-table, it
will unevitably call into __pti_set_user_pgtbl(), which
writes beyond the allocated 4k page.

Use PGD_ALLOCATION_ORDER to allocate PGDs in the kexec code
to fix the issue.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: David H. Gutteridge <dhgutteridge@...patico.ca>
Cc: "H . Peter Anvin" <hpa@...or.com>
Cc: linux-mm@...ck.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Brian Gerst <brgerst@...il.com>
Cc: David Laight <David.Laight@...lab.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Eduardo Valentin <eduval@...zon.com>
Cc: Greg KH <gregkh@...uxfoundation.org>
Cc: Will Deacon <will.deacon@....com>
Cc: aliguori@...zon.com
Cc: daniel.gruss@...k.tugraz.at
Cc: hughd@...gle.com
Cc: keescook@...gle.com
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Waiman Long <llong@...hat.com>
Cc: Pavel Machek <pavel@....cz>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: joro@...tes.org
Link: https://lkml.kernel.org/r/1532533683-5988-4-git-send-email-joro@8bytes.org

---
 arch/x86/kernel/machine_kexec_32.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
index d1ab07ec8c9a..5409c2800ab5 100644
--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -56,7 +56,7 @@ static void load_segments(void)

 static void machine_kexec_free_page_tables(struct kimage *image)
 {
-	free_page((unsigned long)image->arch.pgd);
+	free_pages((unsigned long)image->arch.pgd, PGD_ALLOCATION_ORDER);
 	image->arch.pgd = NULL;
 #ifdef CONFIG_X86_PAE
 	free_page((unsigned long)image->arch.pmd0);
@@ -72,7 +72,8 @@ static void machine_kexec_free_page_tables(struct kimage *image)

 static int machine_kexec_alloc_page_tables(struct kimage *image)
 {
-	image->arch.pgd = (pgd_t *)get_zeroed_page(GFP_KERNEL);
+	image->arch.pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
+						    PGD_ALLOCATION_ORDER);
 #ifdef CONFIG_X86_PAE
 	image->arch.pmd0 = (pmd_t *)get_zeroed_page(GFP_KERNEL);
 	image->arch.pmd1 = (pmd_t *)get_zeroed_page(GFP_KERNEL);