linux.git/fs/userfaultfd.c, branch v5.7

userfaultfd: wp: declare _UFFDIO_WRITEPROTECT conditionally

2020-04-07T17:43:40+00:00

Only declare _UFFDIO_WRITEPROTECT if the user specified
UFFDIO_REGISTER_MODE_WP and if all the checks passed.  Then when the user
registers regions with shmem/hugetlbfs we won't expose the new ioctl to
them.  Even with complete anonymous memory range, we'll only expose the
new WP ioctl bit if the register mode has MODE_WP.

Signed-off-by: Peter Xu 
Signed-off-by: Andrew Morton 
Reviewed-by: Mike Rapoport 
Cc: Andrea Arcangeli 
Cc: Bobby Powers 
Cc: Brian Geffon 
Cc: David Hildenbrand 
Cc: Denis Plotnikov 
Cc: "Dr . David Alan Gilbert" 
Cc: Hugh Dickins 
Cc: Jerome Glisse 
Cc: Johannes Weiner 
Cc: "Kirill A . Shutemov" 
Cc: Martin Cracauer 
Cc: Marty McFadden 
Cc: Maya Gokhale 
Cc: Mel Gorman 
Cc: Mike Kravetz 
Cc: Pavel Emelyanov 
Cc: Rik van Riel 
Cc: Shaohua Li 
Link: http://lkml.kernel.org/r/20200220163112.11409-18-peterx@redhat.com
Signed-off-by: Linus Torvalds

userfaultfd: wp: don't wake up when doing write protect

2020-04-07T17:43:39+00:00

It does not make sense to try to wake up any waiting thread when we're
write-protecting a memory region.  Only wake up when resolving a write
protected page fault.

Signed-off-by: Peter Xu 
Signed-off-by: Andrew Morton 
Reviewed-by: Mike Rapoport 
Cc: Andrea Arcangeli 
Cc: Bobby Powers 
Cc: Brian Geffon 
Cc: David Hildenbrand 
Cc: Denis Plotnikov 
Cc: "Dr . David Alan Gilbert" 
Cc: Hugh Dickins 
Cc: Jerome Glisse 
Cc: Johannes Weiner 
Cc: "Kirill A . Shutemov" 
Cc: Martin Cracauer 
Cc: Marty McFadden 
Cc: Maya Gokhale 
Cc: Mel Gorman 
Cc: Mike Kravetz 
Cc: Pavel Emelyanov 
Cc: Rik van Riel 
Cc: Shaohua Li 
Link: http://lkml.kernel.org/r/20200220163112.11409-16-peterx@redhat.com
Signed-off-by: Linus Torvalds

userfaultfd: wp: add the writeprotect API to userfaultfd ioctl

2020-04-07T17:43:39+00:00

Introduce the new uffd-wp APIs for userspace.

Firstly, we'll allow to do UFFDIO_REGISTER with write protection tracking
using the new UFFDIO_REGISTER_MODE_WP flag.  Note that this flag can
co-exist with the existing UFFDIO_REGISTER_MODE_MISSING, in which case the
userspace program can not only resolve missing page faults, and at the
same time tracking page data changes along the way.

Secondly, we introduced the new UFFDIO_WRITEPROTECT API to do page level
write protection tracking.  Note that we will need to register the memory
region with UFFDIO_REGISTER_MODE_WP before that.

[peterx@redhat.com: write up the commit message]
[peterx@redhat.com: remove useless block, write commit message, check against
 VM_MAYWRITE rather than VM_WRITE when register]
Signed-off-by: Andrea Arcangeli 
Signed-off-by: Peter Xu 
Signed-off-by: Andrew Morton 
Reviewed-by: Jerome Glisse 
Cc: Bobby Powers 
Cc: Brian Geffon 
Cc: David Hildenbrand 
Cc: Denis Plotnikov 
Cc: "Dr . David Alan Gilbert" 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: "Kirill A . Shutemov" 
Cc: Martin Cracauer 
Cc: Marty McFadden 
Cc: Maya Gokhale 
Cc: Mel Gorman 
Cc: Mike Kravetz 
Cc: Mike Rapoport 
Cc: Pavel Emelyanov 
Cc: Rik van Riel 
Cc: Shaohua Li 
Link: http://lkml.kernel.org/r/20200220163112.11409-14-peterx@redhat.com
Signed-off-by: Linus Torvalds

userfaultfd: wp: add UFFDIO_COPY_MODE_WP

2020-04-07T17:43:39+00:00

This allows UFFDIO_COPY to map pages write-protected.

[peterx@redhat.com: switch to VM_WARN_ON_ONCE in mfill_atomic_pte; add brackets
 around "dst_vma->vm_flags & VM_WRITE"; fix wordings in comments and
 commit messages]
Signed-off-by: Andrea Arcangeli 
Signed-off-by: Peter Xu 
Signed-off-by: Andrew Morton 
Reviewed-by: Jerome Glisse 
Reviewed-by: Mike Rapoport 
Cc: Bobby Powers 
Cc: Brian Geffon 
Cc: David Hildenbrand 
Cc: Denis Plotnikov 
Cc: "Dr . David Alan Gilbert" 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: "Kirill A . Shutemov" 
Cc: Martin Cracauer 
Cc: Marty McFadden 
Cc: Maya Gokhale 
Cc: Mel Gorman 
Cc: Mike Kravetz 
Cc: Pavel Emelyanov 
Cc: Rik van Riel 
Cc: Shaohua Li 
Link: http://lkml.kernel.org/r/20200220163112.11409-6-peterx@redhat.com
Signed-off-by: Linus Torvalds

mm/userfaultfd: honor FAULT_FLAG_KILLABLE in fault path

2020-04-02T16:35:30+00:00

Userfaultfd fault path was by default killable even if the caller does not
have FAULT_FLAG_KILLABLE.  That makes sense before in that when with gup
we don't have FAULT_FLAG_KILLABLE properly set before.  Now after previous
patch we've got FAULT_FLAG_KILLABLE applied even for gup code so it should
also make sense to let userfaultfd to honor the FAULT_FLAG_KILLABLE.

Because we're unconditionally setting FAULT_FLAG_KILLABLE in gup code
right now, this patch should have no functional change.  It also cleaned
the code a little bit by introducing some helpers.

Signed-off-by: Peter Xu 
Signed-off-by: Andrew Morton 
Tested-by: Brian Geffon 
Cc: Andrea Arcangeli 
Cc: Bobby Powers 
Cc: David Hildenbrand 
Cc: Denis Plotnikov 
Cc: "Dr . David Alan Gilbert" 
Cc: Hugh Dickins 
Cc: Jerome Glisse 
Cc: Johannes Weiner 
Cc: "Kirill A . Shutemov" 
Cc: Martin Cracauer 
Cc: Marty McFadden 
Cc: Matthew Wilcox 
Cc: Maya Gokhale 
Cc: Mel Gorman 
Cc: Mike Kravetz 
Cc: Mike Rapoport 
Cc: Pavel Emelyanov 
Link: http://lkml.kernel.org/r/20200220160300.9941-1-peterx@redhat.com
Signed-off-by: Linus Torvalds

mm: introduce FAULT_FLAG_INTERRUPTIBLE

2020-04-02T16:35:30+00:00

handle_userfaultfd() is currently the only one place in the kernel page
fault procedures that can respond to non-fatal userspace signals.  It was
trying to detect such an allowance by checking against USER & KILLABLE
flags, which was "un-official".

In this patch, we introduced a new flag (FAULT_FLAG_INTERRUPTIBLE) to show
that the fault handler allows the fault procedure to respond even to
non-fatal signals.  Meanwhile, add this new flag to the default fault
flags so that all the page fault handlers can benefit from the new flag.
With that, replacing the userfault check to this one.

Since the line is getting even longer, clean up the fault flags a bit too
to ease TTY users.

Although we've got a new flag and applied it, we shouldn't have any
functional change with this patch so far.

Suggested-by: Linus Torvalds 
Signed-off-by: Peter Xu 
Signed-off-by: Andrew Morton 
Tested-by: Brian Geffon 
Reviewed-by: David Hildenbrand 
Cc: Andrea Arcangeli 
Cc: Bobby Powers 
Cc: Denis Plotnikov 
Cc: "Dr . David Alan Gilbert" 
Cc: Hugh Dickins 
Cc: Jerome Glisse 
Cc: Johannes Weiner 
Cc: "Kirill A . Shutemov" 
Cc: Martin Cracauer 
Cc: Marty McFadden 
Cc: Matthew Wilcox 
Cc: Maya Gokhale 
Cc: Mel Gorman 
Cc: Mike Kravetz 
Cc: Mike Rapoport 
Cc: Pavel Emelyanov 
Link: http://lkml.kernel.org/r/20200220195348.16302-1-peterx@redhat.com
Signed-off-by: Linus Torvalds

userfaultfd: don't retake mmap_sem to emulate NOPAGE

2020-04-02T16:35:29+00:00

This patch removes the risk path in handle_userfault() then we will be
sure that the callers of handle_mm_fault() will know that the VMAs might
have changed.  Meanwhile with previous patch we don't lose responsiveness
as well since the core mm code now can handle the nonfatal userspace
signals even if we return VM_FAULT_RETRY.

Suggested-by: Andrea Arcangeli 
Suggested-by: Linus Torvalds 
Signed-off-by: Peter Xu 
Signed-off-by: Andrew Morton 
Tested-by: Brian Geffon 
Reviewed-by: Jerome Glisse 
Cc: Bobby Powers 
Cc: David Hildenbrand 
Cc: Denis Plotnikov 
Cc: "Dr . David Alan Gilbert" 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: "Kirill A . Shutemov" 
Cc: Martin Cracauer 
Cc: Marty McFadden 
Cc: Matthew Wilcox 
Cc: Maya Gokhale 
Cc: Mel Gorman 
Cc: Mike Kravetz 
Cc: Mike Rapoport 
Cc: Pavel Emelyanov 
Link: http://lkml.kernel.org/r/20200220160234.9646-1-peterx@redhat.com
Signed-off-by: Linus Torvalds

Merge branch 'akpm' (patches from Andrew)

2019-12-02T04:36:41+00:00

Merge updates from Andrew Morton:
 "Incoming:

   - a small number of updates to scripts/, ocfs2 and fs/buffer.c

   - most of MM

  I still have quite a lot of material (mostly not MM) staged after
  linux-next due to -next dependencies. I'll send those across next week
  as the preprequisites get merged up"

* emailed patches from Andrew Morton : (135 commits)
  mm/page_io.c: annotate refault stalls from swap_readpage
  mm/Kconfig: fix trivial help text punctuation
  mm/Kconfig: fix indentation
  mm/memory_hotplug.c: remove __online_page_set_limits()
  mm: fix typos in comments when calling __SetPageUptodate()
  mm: fix struct member name in function comments
  mm/shmem.c: cast the type of unmap_start to u64
  mm: shmem: use proper gfp flags for shmem_writepage()
  mm/shmem.c: make array 'values' static const, makes object smaller
  userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK
  fs/userfaultfd.c: wp: clear VM_UFFD_MISSING or VM_UFFD_WP during userfaultfd_register()
  userfaultfd: wrap the common dst_vma check into an inlined function
  userfaultfd: remove unnecessary WARN_ON() in __mcopy_atomic_hugetlb()
  userfaultfd: use vma_pagesize for all huge page size calculation
  mm/madvise.c: use PAGE_ALIGN[ED] for range checking
  mm/madvise.c: replace with page_size() in madvise_inject_error()
  mm/mmap.c: make vma_merge() comment more easy to understand
  mm/hwpoison-inject: use DEFINE_DEBUGFS_ATTRIBUTE to define debugfs fops
  autonuma: reduce cache footprint when scanning page tables
  autonuma: fix watermark checking in migrate_balanced_pgdat()
  ...

userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK

2019-12-01T20:59:10+00:00

A while ago Andy noticed
(http://lkml.kernel.org/r/CALCETrWY+5ynDct7eU_nDUqx=okQvjm=Y5wJvA4ahBja=CQXGw@mail.gmail.com)
that UFFD_FEATURE_EVENT_FORK used by an unprivileged user may have
security implications.

As the first step of the solution the following patch limits the availably
of UFFD_FEATURE_EVENT_FORK only for those having CAP_SYS_PTRACE.

The usage of CAP_SYS_PTRACE ensures compatibility with CRIU.

Yet, if there are other users of non-cooperative userfaultfd that run
without CAP_SYS_PTRACE, they would be broken :(

Current implementation of UFFD_FEATURE_EVENT_FORK modifies the file
descriptor table from the read() implementation of uffd, which may have
security implications for unprivileged use of the userfaultfd.

Limit availability of UFFD_FEATURE_EVENT_FORK only for callers that have
CAP_SYS_PTRACE.

Link: http://lkml.kernel.org/r/1572967777-8812-2-git-send-email-rppt@linux.ibm.com
Signed-off-by: Mike Rapoport 
Reviewed-by: Andrea Arcangeli 
Cc: Daniel Colascione 
Cc: Jann Horn 
Cc: Lokesh Gidra 
Cc: Nick Kralevich 
Cc: Nosh Minwalla 
Cc: Pavel Emelyanov 
Cc: Tim Murray 
Cc: Aleksa Sarai 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fs/userfaultfd.c: wp: clear VM_UFFD_MISSING or VM_UFFD_WP during userfaultfd_register()

2019-12-01T20:59:10+00:00

If the registration is repeated without VM_UFFD_MISSING or VM_UFFD_WP they
need to be cleared.  Currently setting UFFDIO_REGISTER_MODE_WP returns
-EINVAL, so this patch is a noop until the UFFDIO_REGISTER_MODE_WP support
is applied.

Link: http://lkml.kernel.org/r/20191004232834.GP13922@redhat.com
Signed-off-by: Andrea Arcangeli 
Reported-by: Wei Yang 
Reviewed-by: Wei Yang 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds