[tip:x86/asm] x86/mm/xen: Suppress hugetlbfs in PV guests

[tip:x86/asm] x86/mm/xen: Suppress hugetlbfs in PV guests

[tip-bot for Jan Beulich]

Commit-ID:  103f6112f253017d7062cd74d17f4a514ed4485c
Gitweb:     http://git.kernel.org/tip/103f6112f253017d7062cd74d17f4a514ed4485c
Author:     Jan Beulich <JBeulich@suse.com>
AuthorDate: Thu, 21 Apr 2016 00:27:04 -0600
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 22 Apr 2016 10:05:00 +0200

x86/mm/xen: Suppress hugetlbfs in PV guests

Huge pages are not normally available to PV guests. Not suppressing
hugetlbfs use results in an endless loop of page faults when user mode
code tries to access a hugetlbfs mapped area (since the hypervisor
denies such PTEs to be created, but error indications can't be
propagated out of xen_set_pte_at(), just like for various of its
siblings), and - once killed in an oops like this:

  kernel BUG at .../fs/hugetlbfs/inode.c:428!
  invalid opcode: 0000 [#1] SMP
  ...
  RIP: e030:[<ffffffff811c333b>]  [<ffffffff811c333b>] remove_inode_hugepages+0x25b/0x320
  ...
  Call Trace:
   [<ffffffff811c3415>] hugetlbfs_evict_inode+0x15/0x40
   [<ffffffff81167b3d>] evict+0xbd/0x1b0
   [<ffffffff8116514a>] __dentry_kill+0x19a/0x1f0
   [<ffffffff81165b0e>] dput+0x1fe/0x220
   [<ffffffff81150535>] __fput+0x155/0x200
   [<ffffffff81079fc0>] task_work_run+0x60/0xa0
   [<ffffffff81063510>] do_exit+0x160/0x400
   [<ffffffff810637eb>] do_group_exit+0x3b/0xa0
   [<ffffffff8106e8bd>] get_signal+0x1ed/0x470
   [<ffffffff8100f854>] do_signal+0x14/0x110
   [<ffffffff810030e9>] prepare_exit_to_usermode+0xe9/0xf0
   [<ffffffff814178a5>] retint_user+0x8/0x13

This is CVE-2016-3961 / XSA-174.

Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <JGross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: stable@vger.kernel.org
Cc: xen-devel <xen-devel@lists.xenproject.org>
Link: http://lkml.kernel.org/r/57188ED802000078000E431C@prv-mh.provo.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/hugetlb.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/hugetlb.h b/arch/x86/include/asm/hugetlb.h
index f8a29d2..e6a8613 100644
--- a/arch/x86/include/asm/hugetlb.h
+++ b/arch/x86/include/asm/hugetlb.h
@@ -4,6 +4,7 @@
 #include <asm/page.h>
 #include <asm-generic/hugetlb.h>
 
+#define hugepages_supported() cpu_has_pse
 
 static inline int is_hugepage_only_range(struct mm_struct *mm,
 					 unsigned long addr,

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Re: [tip:x86/asm] x86/mm/xen: Suppress hugetlbfs in PV guests

[H. Peter Anvin]

On 04/22/2016 02:47 AM, tip-bot for Jan Beulich wrote:
> Commit-ID:  103f6112f253017d7062cd74d17f4a514ed4485c
> Gitweb:     http://git.kernel.org/tip/103f6112f253017d7062cd74d17f4a514ed4485c
> Author:     Jan Beulich <JBeulich@suse.com>
> AuthorDate: Thu, 21 Apr 2016 00:27:04 -0600
> Committer:  Ingo Molnar <mingo@kernel.org>
> CommitDate: Fri, 22 Apr 2016 10:05:00 +0200
> 
> 
> diff --git a/arch/x86/include/asm/hugetlb.h b/arch/x86/include/asm/hugetlb.h
> index f8a29d2..e6a8613 100644
> --- a/arch/x86/include/asm/hugetlb.h
> +++ b/arch/x86/include/asm/hugetlb.h
> @@ -4,6 +4,7 @@
>  #include <asm/page.h>
>  #include <asm-generic/hugetlb.h>
>  
> +#define hugepages_supported() cpu_has_pse
>  

Please don't use the cpu_has_* macros anymore, they are going away soon.

In this case it should be static_cpu_has(X86_FEATURE_PSE).

	-hpa



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Re: [tip:x86/asm] x86/mm/xen: Suppress hugetlbfs in PV guests

[Borislav Petkov]

On Fri, Apr 22, 2016 at 11:03:53AM -0700, H. Peter Anvin wrote:
> Please don't use the cpu_has_* macros anymore, they are going away soon.
> 
> In this case it should be static_cpu_has(X86_FEATURE_PSE).

Ingo fixed this up while merging:

b2eafe890d4a ("Merge branch 'x86/urgent' into x86/asm, to fix semantic conflict")

The cpu_has_* things are gone now in tip! \o/

:-)

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

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Re: [tip:x86/asm] x86/mm/xen: Suppress hugetlbfs in PV guests

[Jan Beulich]

>>> On 22.04.16 at 20:03, <hpa@zytor.com> wrote:
> On 04/22/2016 02:47 AM, tip-bot for Jan Beulich wrote:
>> Commit-ID:  103f6112f253017d7062cd74d17f4a514ed4485c
>> Gitweb:     
> http://git.kernel.org/tip/103f6112f253017d7062cd74d17f4a514ed4485c 
>> Author:     Jan Beulich <JBeulich@suse.com>
>> AuthorDate: Thu, 21 Apr 2016 00:27:04 -0600
>> Committer:  Ingo Molnar <mingo@kernel.org>
>> CommitDate: Fri, 22 Apr 2016 10:05:00 +0200
>> 
>> 
>> diff --git a/arch/x86/include/asm/hugetlb.h b/arch/x86/include/asm/hugetlb.h
>> index f8a29d2..e6a8613 100644
>> --- a/arch/x86/include/asm/hugetlb.h
>> +++ b/arch/x86/include/asm/hugetlb.h
>> @@ -4,6 +4,7 @@
>>  #include <asm/page.h>
>>  #include <asm-generic/hugetlb.h>
>>  
>> +#define hugepages_supported() cpu_has_pse
>>  
> 
> Please don't use the cpu_has_* macros anymore, they are going away soon.
> 
> In this case it should be static_cpu_has(X86_FEATURE_PSE).

I can certainly do that, but this
- will (mildly) harm backportability
- imo should have been requested much earlier (when the patch was
  still under discussion)

Jan


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Re: [tip:x86/asm] x86/mm/xen: Suppress hugetlbfs in PV guests

[Thomas Gleixner]

On Mon, 25 Apr 2016, Jan Beulich wrote:
> >>> On 22.04.16 at 20:03, <hpa@zytor.com> wrote:
> >> +#define hugepages_supported() cpu_has_pse
> >>  
> > 
> > Please don't use the cpu_has_* macros anymore, they are going away soon.
> > 
> > In this case it should be static_cpu_has(X86_FEATURE_PSE).
> 
> I can certainly do that, but this
> - will (mildly) harm backportability
> - imo should have been requested much earlier (when the patch was
>   still under discussion)

It's requested now as cpu_has_* is going away. So instead of making silly
arguments you should have sent a delta patch fixing this.

Thanks,

	tglx

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Re: [tip:x86/asm] x86/mm/xen: Suppress hugetlbfs in PV guests

[David Vrabel]

On 25/04/16 08:52, Thomas Gleixner wrote:
> On Mon, 25 Apr 2016, Jan Beulich wrote:
>>>>> On 22.04.16 at 20:03, <hpa@zytor.com> wrote:
>>>> +#define hugepages_supported() cpu_has_pse
>>>>  
>>>
>>> Please don't use the cpu_has_* macros anymore, they are going away soon.
>>>
>>> In this case it should be static_cpu_has(X86_FEATURE_PSE).
>>
>> I can certainly do that, but this
>> - will (mildly) harm backportability
>> - imo should have been requested much earlier (when the patch was
>>   still under discussion)
> 
> It's requested now as cpu_has_* is going away. So instead of making silly
> arguments you should have sent a delta patch fixing this.

Ingo fixed this up in the x86/asm branch[1] so I assumed this patch
didn't need updating.

David

[1]
https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/commit/?h=x86/asm&id=b2eafe890d4a09bfa63ab31ff018d7d6bb8cfefc

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