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 7wLb9v5l 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: * Peter Xu [230517 11:04]: > 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). > > Cc: Andrea Arcangeli > Cc: Mike Rapoport (IBM) > Cc: linux-stable > Fixes: 86039bd3b4e6 ("userfaultfd: add new syscall to provide memory externalization") > Signed-off-by: Peter Xu Reviewed-by: Liam R. Howlett > --- > fs/userfaultfd.c | 8 ++++++-- > 1 file 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) { > -- > 2.39.1 >