Commit 27d02568 authored by Mike Rapoport's avatar Mike Rapoport Committed by Linus Torvalds
Browse files

userfaultfd: mcopy_atomic: return -ENOENT when no compatible VMA found

The memory mapping of a process may change between #PF event and the
call to mcopy_atomic that comes to resolve the page fault.  In such
case, there will be no VMA covering the range passed to mcopy_atomic or
the VMA will not have userfaultfd context.

To allow uffd monitor to distinguish those case from other errors, let's
return -ENOENT instead of -EINVAL.

Note, that despite availability of UFFD_EVENT_UNMAP there still might be
race between the processing of UFFD_EVENT_UNMAP and outstanding
mcopy_atomic in case of non-cooperative uffd usage.

[rppt@linux.vnet.ibm.com: update cases returning -ENOENT]
  Link: http://lkml.kernel.org/r/20170207150249.GA6709@rapoport-lnx
[aarcange@redhat.com: merge fix]
[akpm@linux-foundation.org: fix the merge fix]
Link: http://lkml.kernel.org/r/1485542673-24387-5-git-send-email-rppt@linux.vnet.ibm.com

Signed-off-by: default avatarMike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: default avatarHillf Danton <hillf.zj@alibaba-inc.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ca49ca71
......@@ -197,22 +197,25 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
* retry, dst_vma will be set to NULL and we must lookup again.
*/
if (!dst_vma) {
err = -EINVAL;
err = -ENOENT;
dst_vma = find_vma(dst_mm, dst_start);
if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
goto out_unlock;
if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
goto out_unlock;
/*
* Make sure the remaining dst range is both valid and
* fully within a single existing vma.
* Only allow __mcopy_atomic_hugetlb on userfaultfd
* registered ranges.
*/
if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;
if (dst_start < dst_vma->vm_start ||
dst_start + len > dst_vma->vm_end)
goto out_unlock;
err = -EINVAL;
if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
goto out_unlock;
vm_shared = dst_vma->vm_flags & VM_SHARED;
}
......@@ -220,12 +223,6 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
(len - copied) & (vma_hpagesize - 1)))
goto out_unlock;
/*
* Only allow __mcopy_atomic_hugetlb on userfaultfd registered ranges.
*/
if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;
/*
* If not shared, ensure the dst_vma has a anon_vma.
*/
......@@ -404,22 +401,35 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
* Make sure the vma is not shared, that the dst range is
* both valid and fully within a single existing vma.
*/
err = -EINVAL;
err = -ENOENT;
dst_vma = find_vma(dst_mm, dst_start);
if (!dst_vma)
goto out_unlock;
/*
* shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
* it will overwrite vm_ops, so vma_is_anonymous must return false.
* Be strict and only allow __mcopy_atomic on userfaultfd
* registered ranges to prevent userland errors going
* unnoticed. As far as the VM consistency is concerned, it
* would be perfectly safe to remove this check, but there's
* no useful usage for __mcopy_atomic ouside of userfaultfd
* registered ranges. This is after all why these are ioctls
* belonging to the userfaultfd and not syscalls.
*/
if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
dst_vma->vm_flags & VM_SHARED))
if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;
if (dst_start < dst_vma->vm_start ||
dst_start + len > dst_vma->vm_end)
goto out_unlock;
err = -EINVAL;
/*
* shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
* it will overwrite vm_ops, so vma_is_anonymous must return false.
*/
if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
dst_vma->vm_flags & VM_SHARED))
goto out_unlock;
/*
* If this is a HUGETLB vma, pass off to appropriate routine
*/
......@@ -427,18 +437,6 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
src_start, len, zeropage);
/*
* Be strict and only allow __mcopy_atomic on userfaultfd
* registered ranges to prevent userland errors going
* unnoticed. As far as the VM consistency is concerned, it
* would be perfectly safe to remove this check, but there's
* no useful usage for __mcopy_atomic ouside of userfaultfd
* registered ranges. This is after all why these are ioctls
* belonging to the userfaultfd and not syscalls.
*/
if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;
if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
goto out_unlock;
......
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