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Patch "x86/mm/xen: Suppress hugetlbfs in PV guests" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message May 1, 2016

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

x86/mm/xen: Suppress hugetlbfs in PV guests

to the 4.4-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-mm-xen-suppress-hugetlbfs-in-pv-guests.patch
and it can be found in the queue-4.4 subdirectory.

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

Quoted 1 line

From 103f6112f253017d7062cd74d17f4a514ed4485c Mon Sep 17 00:00:00 2001

From: Jan Beulich <[email protected]>
Date: Thu, 21 Apr 2016 00:27:04 -0600
Subject: x86/mm/xen: Suppress hugetlbfs in PV guests

From: Jan Beulich <[email protected]>

commit 103f6112f253017d7062cd74d17f4a514ed4485c upstream.

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 <[email protected]>
Signed-off-by Jan Beulich <[email protected]>
Cc Andrew Morton <[email protected]>
Cc Andy Lutomirski <[email protected]>
Cc Boris Ostrovsky <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc Brian Gerst <[email protected]>
Cc David Vrabel <[email protected]>
Cc Denys Vlasenko <[email protected]>
Cc H. Peter Anvin <[email protected]>
Cc Juergen Gross <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Luis R. Rodriguez <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Thomas Gleixner <[email protected]>
Cc Toshi Kani <[email protected]>
Cc xen-devel <[email protected]>
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Ingo Molnar <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 arch/x86/include/asm/hugetlb.h |    1 +
 1 file changed, 1 insertion(+)
arch/x86/include/asm/hugetlb.h +1 -0
@@ -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,

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/x86-mm-xen-suppress-hugetlbfs-in-pv-guests.patch