[v14,08/17] mm, arm64: untag user pointers in get_vaddr_frames
diff mbox series

Message ID 8e20df035de677029b3f970744ba2d35e2df1db3.1556630205.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.

get_vaddr_frames uses provided user pointers for vma lookups, which can
only by done with untagged pointers. Instead of locating and changing
all callers of this function, perform untagging in it.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/frame_vector.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Catalin Marinas May 3, 2019, 4:51 p.m. UTC | #1
On Tue, Apr 30, 2019 at 03:25:04PM +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.
> 
> get_vaddr_frames uses provided user pointers for vma lookups, which can
> only by done with untagged pointers. Instead of locating and changing
> all callers of this function, perform untagging in it.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
>  mm/frame_vector.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/frame_vector.c b/mm/frame_vector.c
> index c64dca6e27c2..c431ca81dad5 100644
> --- a/mm/frame_vector.c
> +++ b/mm/frame_vector.c
> @@ -46,6 +46,8 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
>  	if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
>  		nr_frames = vec->nr_allocated;
>  
> +	start = untagged_addr(start);
> +
>  	down_read(&mm->mmap_sem);
>  	locked = 1;
>  	vma = find_vma_intersection(mm, start, start + 1);

Is this some buffer that the user may have malloc'ed? I got lost when
trying to track down the provenience of this buffer.
Andrey Konovalov May 6, 2019, 1:53 p.m. UTC | #2
On Fri, May 3, 2019 at 6:51 PM Catalin Marinas <catalin.marinas@arm.com> wrote:
>
> On Tue, Apr 30, 2019 at 03:25:04PM +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.
> >
> > get_vaddr_frames uses provided user pointers for vma lookups, which can
> > only by done with untagged pointers. Instead of locating and changing
> > all callers of this function, perform untagging in it.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > ---
> >  mm/frame_vector.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/mm/frame_vector.c b/mm/frame_vector.c
> > index c64dca6e27c2..c431ca81dad5 100644
> > --- a/mm/frame_vector.c
> > +++ b/mm/frame_vector.c
> > @@ -46,6 +46,8 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
> >       if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
> >               nr_frames = vec->nr_allocated;
> >
> > +     start = untagged_addr(start);
> > +
> >       down_read(&mm->mmap_sem);
> >       locked = 1;
> >       vma = find_vma_intersection(mm, start, start + 1);
>
> Is this some buffer that the user may have malloc'ed? I got lost when
> trying to track down the provenience of this buffer.

The caller that I found when I was looking at this:

drivers/gpu/drm/exynos/exynos_drm_g2d.c:482
exynos_g2d_set_cmdlist_ioctl()->g2d_map_cmdlist_gem()->g2d_userptr_get_dma_addr()->get_vaddr_frames()

>
> --
> Catalin

Patch
diff mbox series

diff --git a/mm/frame_vector.c b/mm/frame_vector.c
index c64dca6e27c2..c431ca81dad5 100644
--- a/mm/frame_vector.c
+++ b/mm/frame_vector.c
@@ -46,6 +46,8 @@  int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 	if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
 		nr_frames = vec->nr_allocated;
 
+	start = untagged_addr(start);
+
 	down_read(&mm->mmap_sem);
 	locked = 1;
 	vma = find_vma_intersection(mm, start, start + 1);