tree 52675652618b2b725b7c01005ce80bbc72769923
parent 484b04309917a82b364e695fdcc3f4fb6b342c06
author Peter Xu <peterx@redhat.com> 1616047306 +1100
committer Tim Zimmermann <tim@linux4.de> 1721966657 +0200
gpgsig -----BEGIN PGP SIGNATURE-----
 
 iQIzBAABCgAdFiEEuwYxAyE4TRnuhLgPbcIaY/gZxe8FAmajIEEACgkQbcIaY/gZ
 xe/G8g/8Cc8ZJHx1bUPeQPChZ7nTk07g6uCgdW60LnLg/EAdiRPcLRviV3YwJLsF
 iXgkJzJtwuzFGQIXSOyhFnW8XkK2nW/jRHtz54/ktbTA5lZRbsE9I+HJHXk5qEBF
 XFFYP5Po2ZM7fy/+WYIT/v3Cw0AjBTkbnHWj3mBBOfeq+FIR0sbsiuzhJa1tYWrE
 DT18uqe4etP5FwlzB53NgJIznXYbhQTqxuR/UHnOC8Of+tIfFKtyqohlt31sQuCz
 S9QJ4YUlR9jxDMsufs7h3T0QaUNT7r/39fYO3qraRmts7WDXWb3VRFUpbNrHFXcC
 7y1jzDujFAe90xHhLG/qks1PuYLk5cDR3k6ZCc9lRK7rMaAXMjy1wZHUTiQcvtK+
 BAYjnWQxs6QwZRugqRNt1NzKc++p+JbLhCy+LGPBQQpMrayMN24/GMjDohF8hbqA
 NfVdoXGuM3X6xRrDFDj1pgEmoaesVGxI48ueXM5IfMDk8vbPDQktQmBZefS7gUrK
 qApUo2JyQ/UQ3pqimmc5rS6AnItueDPiw+84kMw5s5T0j9Vpys1Xjto1b1UV7ksK
 5CYeLuAxZR7wCvEyVOVC4FtwHLd1igaGqVeNndOq3aUoFp/EU3v7nbxKdOJ6uprf
 fxX/ZbQM2s/YCqoGpmOnM8Ar9AfMVZrGcZ5thpZ61dWmoRUedMA=
 =R8g8
 -----END PGP SIGNATURE-----

BACKPORT: FROMGIT: hugetlb/userfaultfd: forbid huge pmd sharing when uffd enabled

Huge pmd sharing could bring problem to userfaultfd.  The thing is that
userfaultfd is running its logic based on the special bits on page table
entries, however the huge pmd sharing could potentially share page table
entries for different address ranges.  That could cause issues on either:

  - When sharing huge pmd page tables for an uffd write protected range, the
    newly mapped huge pmd range will also be write protected unexpectedly, or,

  - When we try to write protect a range of huge pmd shared range, we'll first
    do huge_pmd_unshare() in hugetlb_change_protection(), however that also
    means the UFFDIO_WRITEPROTECT could be silently skipped for the shared
    region, which could lead to data loss.

Since at it, a few other things are done altogether:

  - Move want_pmd_share() from mm/hugetlb.c into linux/hugetlb.h, because
    that's definitely something that arch code would like to use too

  - ARM64 currently directly check against CONFIG_ARCH_WANT_HUGE_PMD_SHARE when
    trying to share huge pmd.  Switch to the want_pmd_share() helper.

Since at it, move vma_shareable() from huge_pmd_share() into want_pmd_share().

Link: https://lkml.kernel.org/r/20210218231202.15426-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Price <steven.price@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

(cherry picked from commit ab6a0d00a63f92f1f0d220274fa989eb75c09f2b
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm)
Link: https://lore.kernel.org/patchwork/patch/1382207/
Conflicts:
	include/linux/hugetlb.h
	mm/hugetlb.c

(Manual rebase)

Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Bug: 160737021
Bug: 169683130
Change-Id: Ie2dff7ab31600cae78914e3278be61516844394e