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    SubjectRe: [PATCH v18 08/15] userfaultfd: untag user pointers
    On Mon, Jun 24, 2019 at 7:51 PM Catalin Marinas <catalin.marinas@arm.com> 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.

    Hi Al,

    Could you take a look at this one as well and give your acked-by?

    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

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