On Tue, Apr 30, 2019 at 03:25:06PM +0200, Andrey Konovalov wrote: > This patch is a part of a series that extends arm64 kernel ABI to allow to > pass tagged user pointers (with the top byte set to something else other > than 0x00) as syscall arguments. > > userfaultfd_register() and userfaultfd_unregister() use provided user > pointers for vma lookups, which can only by done with untagged pointers. > > Untag user pointers in these functions. > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > --- > fs/userfaultfd.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index f5de1e726356..fdee0db0e847 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -1325,6 +1325,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, > goto out; > } > > + uffdio_register.range.start = > + untagged_addr(uffdio_register.range.start); > + > ret = validate_range(mm, uffdio_register.range.start, > uffdio_register.range.len); > if (ret) > @@ -1514,6 +1517,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, > if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) > goto out; > > + uffdio_unregister.start = untagged_addr(uffdio_unregister.start); > + > ret = validate_range(mm, uffdio_unregister.start, > uffdio_unregister.len); > if (ret) Wouldn't it be easier to do this in validate_range()? There are a few more calls in this file, though I didn't check whether a tagged address would cause issues. -- Catalin
