Patch "x86/kexec: Allocate 8k PGDs for PTI" has been added to the 3.18-stable tree

Commit Message

Greg Kroah-Hartman Sept. 17, 2018, 9:46 a.m. UTC

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

    x86/kexec: Allocate 8k PGDs for PTI

to the 3.18-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-kexec-allocate-8k-pgds-for-pti.patch
and it can be found in the queue-3.18 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 Mon Sep 17 11:45:57 CEST 2018
From: Joerg Roedel <[e-mail]>
Date: Wed, 25 Jul 2018 17:48:03 +0200
Subject: x86/kexec: Allocate 8k PGDs for PTI

From: Joerg Roedel <[e-mail]>

[ Upstream commit ca38dc8f2724d101038b1205122c93a1c7f38f11 ]

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 <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Tested-by: David H. Gutteridge <[e-mail]>
Cc: "H . Peter Anvin" <[e-mail]>
Cc: [e-mail]
Cc: Linus Torvalds <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Josh Poimboeuf <[e-mail]>
Cc: Juergen Gross <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Jiri Kosina <[e-mail]>
Cc: Boris Ostrovsky <[e-mail]>
Cc: Brian Gerst <[e-mail]>
Cc: David Laight <[e-mail]>
Cc: Denys Vlasenko <[e-mail]>
Cc: Eduardo Valentin <[e-mail]>
Cc: Greg KH <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: Andrea Arcangeli <[e-mail]>
Cc: Waiman Long <[e-mail]>
Cc: Pavel Machek <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: [e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Sasha Levin <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>
---
 arch/x86/kernel/machine_kexec_32.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)



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

queue-3.18/x86-kexec-allocate-8k-pgds-for-pti.patch
queue-3.18/x86-mm-remove-in_nmi-warning-from-vmalloc_fault.patch

Comments

Hugh Dickins Sept. 17, 2018, 7:33 p.m. UTC | #1

On Mon, 17 Sep 2018, [e-mail] wrote:
> 
> This is a note to let you know that I've just added the patch titled
> 
>     x86/kexec: Allocate 8k PGDs for PTI
> 
> to the 3.18-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-kexec-allocate-8k-pgds-for-pti.patch
> and it can be found in the queue-3.18 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <[e-mail]> know about it.

I believe this commit is an example of the auto-selector being too
eager, and this should not be in *any* of the stable trees.  As the
commit message indicates, it's a fix by Joerg for his PTI-x86-32
implementation - which has not been backported to any of the stable
trees (yet), has it?

In several of the recent stable trees, I think this will not do any
actual harm; but it looks as if it will prevent relevant x86-32 configs
from building on 3.18 (I see no definition of PGD_ALLOCATION_ORDER in
linux-3.18.y - you preferred not to have any PTI in that tree), and I
haven't checked whether its definition in older backports will build
correctly here or not.

Hugh

> 
> 
> From foo@baz Mon Sep 17 11:45:57 CEST 2018
> From: Joerg Roedel <[e-mail]>
> Date: Wed, 25 Jul 2018 17:48:03 +0200
> Subject: x86/kexec: Allocate 8k PGDs for PTI
> 
> From: Joerg Roedel <[e-mail]>
> 
> [ Upstream commit ca38dc8f2724d101038b1205122c93a1c7f38f11 ]
> 
> 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 <[e-mail]>
> Signed-off-by: Thomas Gleixner <[e-mail]>
> Tested-by: David H. Gutteridge <[e-mail]>
> Cc: "H . Peter Anvin" <[e-mail]>
> Cc: [e-mail]
> Cc: Linus Torvalds <[e-mail]>
> Cc: Andy Lutomirski <[e-mail]>
> Cc: Dave Hansen <[e-mail]>
> Cc: Josh Poimboeuf <[e-mail]>
> Cc: Juergen Gross <[e-mail]>
> Cc: Peter Zijlstra <[e-mail]>
> Cc: Borislav Petkov <[e-mail]>
> Cc: Jiri Kosina <[e-mail]>
> Cc: Boris Ostrovsky <[e-mail]>
> Cc: Brian Gerst <[e-mail]>
> Cc: David Laight <[e-mail]>
> Cc: Denys Vlasenko <[e-mail]>
> Cc: Eduardo Valentin <[e-mail]>
> Cc: Greg KH <[e-mail]>
> Cc: Will Deacon <[e-mail]>
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: Andrea Arcangeli <[e-mail]>
> Cc: Waiman Long <[e-mail]>
> Cc: Pavel Machek <[e-mail]>
> Cc: Arnaldo Carvalho de Melo <[e-mail]>
> Cc: Alexander Shishkin <[e-mail]>
> Cc: Jiri Olsa <[e-mail]>
> Cc: Namhyung Kim <[e-mail]>
> Cc: [e-mail]
> Link: https://lkml.kernel.org/r/[e-mail]
> Signed-off-by: Sasha Levin <[e-mail]>
> Signed-off-by: Greg Kroah-Hartman <[e-mail]>
> ---
>  arch/x86/kernel/machine_kexec_32.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> --- a/arch/x86/kernel/machine_kexec_32.c
> +++ b/arch/x86/kernel/machine_kexec_32.c
> @@ -69,7 +69,7 @@ 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);
> @@ -85,7 +85,8 @@ static void machine_kexec_free_page_tabl
>  
>  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);
> 
> 
> Patches currently in stable-queue which might be from [e-mail] are
> 
> queue-3.18/x86-kexec-allocate-8k-pgds-for-pti.patch
> queue-3.18/x86-mm-remove-in_nmi-warning-from-vmalloc_fault.patch
>

Greg Kroah-Hartman Sept. 17, 2018, 8:22 p.m. UTC | #2

On Mon, Sep 17, 2018 at 12:33:47PM -0700, Hugh Dickins wrote:
> On Mon, 17 Sep 2018, [e-mail] wrote:
> > 
> > This is a note to let you know that I've just added the patch titled
> > 
> >     x86/kexec: Allocate 8k PGDs for PTI
> > 
> > to the 3.18-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-kexec-allocate-8k-pgds-for-pti.patch
> > and it can be found in the queue-3.18 subdirectory.
> > 
> > If you, or anyone else, feels it should not be added to the stable tree,
> > please let <[e-mail]> know about it.
> 
> I believe this commit is an example of the auto-selector being too
> eager, and this should not be in *any* of the stable trees.  As the
> commit message indicates, it's a fix by Joerg for his PTI-x86-32
> implementation - which has not been backported to any of the stable
> trees (yet), has it?
> 
> In several of the recent stable trees, I think this will not do any
> actual harm; but it looks as if it will prevent relevant x86-32 configs
> from building on 3.18 (I see no definition of PGD_ALLOCATION_ORDER in
> linux-3.18.y - you preferred not to have any PTI in that tree), and I
> haven't checked whether its definition in older backports will build
> correctly here or not.

Ah, you are right, I just got a build failure report from the 4.4.y tree
with this exact error.

Thanks for letting me know, I'll go drop this from all of the stable
tree queues right now.

greg k-h

Joerg Roedel Sept. 17, 2018, 9:09 p.m. UTC | #3

On Mon, Sep 17, 2018 at 12:33:47PM -0700, Hugh Dickins wrote:
> In several of the recent stable trees, I think this will not do any
> actual harm; but it looks as if it will prevent relevant x86-32 configs
> from building on 3.18 (I see no definition of PGD_ALLOCATION_ORDER in
> linux-3.18.y - you preferred not to have any PTI in that tree), and I
> haven't checked whether its definition in older backports will build
> correctly here or not.

Right, thanks for pointing that out. I should have added a Fixes:-tag to
the patch to make clear what the fix it for, sorry for that.


	Joerg

Patch

--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -69,7 +69,7 @@  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);
@@ -85,7 +85,8 @@  static void machine_kexec_free_page_tabl
 
 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);