diff options
| author | Peter Xu <peterx@redhat.com> | 2023-05-17 15:09:16 -0400 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-06-12 11:31:50 -0700 |
| commit | 5543d3c43c41a8501f2a4946d0fd39ce36b5a641 (patch) | |
| tree | f3ef598c5c7bb68e757bc1108eb0a5cd96871849 /fs/userfaultfd.c | |
| parent | 270aa010620697fb27b8f892cc4e194bc2b7d134 (diff) | |
mm/uffd: allow vma to merge as much as possible
We used to not pass in the pgoff correctly when register/unregister uffd
regions, it caused incorrect behavior on vma merging and can cause
mergeable vmas being separate after ioctls return.
For example, when we have:
vma1(range 0-9, with uffd), vma2(range 10-19, no uffd)
Then someone unregisters uffd on range (5-9), it should logically become:
vma1(range 0-4, with uffd), vma2(range 5-19, no uffd)
But with current code we'll have:
vma1(range 0-4, with uffd), vma3(range 5-9, no uffd), vma2(range 10-19, no uffd)
This patch allows such merge to happen correctly before ioctl returns.
This behavior seems to have existed since the 1st day of uffd. Since
pgoff for vma_merge() is only used to identify the possibility of vma
merging, meanwhile here what we did was always passing in a pgoff smaller
than what we should, so there should have no other side effect besides not
merging it. Let's still tentatively copy stable for this, even though I
don't see anything will go wrong besides vma being split (which is mostly
not user visible).
Link: https://lkml.kernel.org/r/20230517190916.3429499-3-peterx@redhat.com
Fixes: 86039bd3b4e6 ("userfaultfd: add new syscall to provide memory externalization")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'fs/userfaultfd.c')
| -rw-r--r-- | fs/userfaultfd.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 17c8c345dac4..4e800bb7d2ab 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1332,6 +1332,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, bool basic_ioctls; unsigned long start, end, vma_end; struct vma_iterator vmi; + pgoff_t pgoff; user_uffdio_register = (struct uffdio_register __user *) arg; @@ -1484,8 +1485,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, vma_end = min(end, vma->vm_end); new_flags = (vma->vm_flags & ~__VM_UFFD_FLAGS) | vm_flags; + pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); prev = vma_merge(&vmi, mm, prev, start, vma_end, new_flags, - vma->anon_vma, vma->vm_file, vma->vm_pgoff, + vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), ((struct vm_userfaultfd_ctx){ ctx }), anon_vma_name(vma)); @@ -1565,6 +1567,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, unsigned long start, end, vma_end; const void __user *buf = (void __user *)arg; struct vma_iterator vmi; + pgoff_t pgoff; ret = -EFAULT; if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) @@ -1667,8 +1670,9 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, uffd_wp_range(vma, start, vma_end - start, false); new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS; + pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); prev = vma_merge(&vmi, mm, prev, start, vma_end, new_flags, - vma->anon_vma, vma->vm_file, vma->vm_pgoff, + vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), NULL_VM_UFFD_CTX, anon_vma_name(vma)); if (prev) { |