[v14,10/17] fs, arm64: untag user pointers in fs/userfaultfd.c
diff mbox series

Message ID 7d3b28689d47c0fa1b80628f248dbf78548da25f.1556630205.git.andreyknvl@google.com
State New
Headers show
Series
  • arm64: untag user pointers passed to the kernel
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Commit Message

Andrey Konovalov April 30, 2019, 1:25 p.m. UTC
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@google.com>
---
 fs/userfaultfd.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Catalin Marinas May 3, 2019, 4:56 p.m. UTC | #1
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@google.com>
> ---
>  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.
Andrey Konovalov May 6, 2019, 2:15 p.m. UTC | #2
On Fri, May 3, 2019 at 6:56 PM Catalin Marinas <catalin.marinas@arm.com> wrote:
>
> 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@google.com>
> > ---
> >  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.

Yes, I think it makes more sense, will do in v15, thanks!

>
> --
> Catalin

Patch
diff mbox series

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)