Re: [PATCH v18 08/15] userfaultfd: untag user pointers

Andrey Konovalov
2019-07-17T11:47:05Z

On Wed, Jul 17, 2019 at 1:09 PM Mike Rapoport <rppt@linux.ibm.com> wrote:
>
> On Mon, Jun 24, 2019 at 06:51:21PM +0100, Catalin Marinas wrote:
> > On Mon, Jun 24, 2019 at 04:32:53PM +0200, Andrey Konovalov wrote:
> > > This patch is a part of a series that extends kernel ABI to allow to pass
> > > tagged user pointers (with the top byte set to something else other than
> > > 0x00) as syscall arguments.
> > >
> > > userfaultfd code use provided user pointers for vma lookups, which can
> > > only by done with untagged pointers.
> > >
> > > Untag user pointers in validate_range().
> > >
> > > Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> > > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> > > Reviewed-by: Kees Cook <keescook@chromium.org>
> > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > > ---
> > > fs/userfaultfd.c | 22 ++++++++++++----------
> > > 1 file changed, 12 insertions(+), 10 deletions(-)
> >
> > Same here, it needs an ack from Al Viro.
>
> The userfault patches usually go via -mm tree, not sure if Al looks at them :)

Ah, OK, I guess than Andrew will take a look at them when merging.

>
> FWIW, you can add
>
> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>

I will, thanks!

>
> > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> > > index ae0b8b5f69e6..c2be36a168ca 100644
> > > --- a/fs/userfaultfd.c
> > > +++ b/fs/userfaultfd.c
> > > @@ -1261,21 +1261,23 @@ static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
> > > }
> > >
> > > static __always_inline int validate_range(struct mm_struct *mm,
> > > - __u64 start, __u64 len)
> > > + __u64 *start, __u64 len)
> > > {
> > > __u64 task_size = mm->task_size;
> > >
> > > - if (start & ~PAGE_MASK)
> > > + *start = untagged_addr(*start);
> > > +
> > > + if (*start & ~PAGE_MASK)
> > > return -EINVAL;
> > > if (len & ~PAGE_MASK)
> > > return -EINVAL;
> > > if (!len)
> > > return -EINVAL;
> > > - if (start < mmap_min_addr)
> > > + if (*start < mmap_min_addr)
> > > return -EINVAL;
> > > - if (start >= task_size)
> > > + if (*start >= task_size)
> > > return -EINVAL;
> > > - if (len > task_size - start)
> > > + if (len > task_size - *start)
> > > return -EINVAL;
> > > return 0;
> > > }
> > > @@ -1325,7 +1327,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
> > > goto out;
> > > }
> > >
> > > - ret = validate_range(mm, uffdio_register.range.start,
> > > + ret = validate_range(mm, &uffdio_register.range.start,
> > > uffdio_register.range.len);
> > > if (ret)
> > > goto out;
> > > @@ -1514,7 +1516,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> > > if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
> > > goto out;
> > >
> > > - ret = validate_range(mm, uffdio_unregister.start,
> > > + ret = validate_range(mm, &uffdio_unregister.start,
> > > uffdio_unregister.len);
> > > if (ret)
> > > goto out;
> > > @@ -1665,7 +1667,7 @@ static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
> > > if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
> > > goto out;
> > >
> > > - ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len);
> > > + ret = validate_range(ctx->mm, &uffdio_wake.start, uffdio_wake.len);
> > > if (ret)
> > > goto out;
> > >
> > > @@ -1705,7 +1707,7 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
> > > sizeof(uffdio_copy)-sizeof(__s64)))
> > > goto out;
> > >
> > > - ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
> > > + ret = validate_range(ctx->mm, &uffdio_copy.dst, uffdio_copy.len);
> > > if (ret)
> > > goto out;
> > > /*
> > > @@ -1761,7 +1763,7 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
> > > sizeof(uffdio_zeropage)-sizeof(__s64)))
> > > goto out;
> > >
> > > - ret = validate_range(ctx->mm, uffdio_zeropage.range.start,
> > > + ret = validate_range(ctx->mm, &uffdio_zeropage.range.start,
> > > uffdio_zeropage.range.len);
> > > if (ret)
> > > goto out;
> > > --
> > > 2.22.0.410.gd8fdbe21b5-goog
>
> --
> Sincerely yours,
> Mike.
>