diff mbox series

drm/vgem: fix use-after-free when drm_gem_handle_create() fails

Message ID 20190226204726.92256-1-ebiggers@kernel.org (mailing list archive)
State New, archived
Headers show
Series drm/vgem: fix use-after-free when drm_gem_handle_create() fails | expand

Commit Message

Eric Biggers Feb. 26, 2019, 8:47 p.m. UTC 
From: Eric Biggers <ebiggers@google.com>

If drm_gem_handle_create() fails in vgem_gem_create(), then the
drm_vgem_gem_object is freed twice: once when the reference is dropped
by drm_gem_object_put_unlocked(), and again by __vgem_gem_destroy().

This was hit by syzkaller using fault injection.

Fix it by skipping the second free.

Reported-by: syzbot+e73f2fb5ed5a5df36d33@syzkaller.appspotmail.com
Fixes: 5ba6c9ff961a ("drm/vgem: Fix mmaping")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 drivers/gpu/drm/vgem/vgem_drv.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

Comments

Chris Wilson Feb. 26, 2019, 9:01 p.m. UTC | #1 
Quoting Eric Biggers (2019-02-26 20:47:26)
> From: Eric Biggers <ebiggers@google.com>
> 
> If drm_gem_handle_create() fails in vgem_gem_create(), then the
> drm_vgem_gem_object is freed twice: once when the reference is dropped
> by drm_gem_object_put_unlocked(), and again by __vgem_gem_destroy().
> 
> This was hit by syzkaller using fault injection.
> 
> Fix it by skipping the second free.
> 
> Reported-by: syzbot+e73f2fb5ed5a5df36d33@syzkaller.appspotmail.com
> Fixes: 5ba6c9ff961a ("drm/vgem: Fix mmaping")

That's the wrong fixes line, it's
Fixes: af33a9190d02 ("drm/vgem: Enable dmabuf import interfaces")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>

Sadly I reviewed it so I'm still culpable, but the fix is correct as the
put purposely frees it on error.

> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>

> ---
>  drivers/gpu/drm/vgem/vgem_drv.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> index 5930facd6d2d8..70646d9da1596 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -189,15 +189,13 @@ static struct drm_gem_object *vgem_gem_create(struct drm_device *dev,
>                 return ERR_CAST(obj);
>  
>         ret = drm_gem_handle_create(file, &obj->base, handle);
> +
>         drm_gem_object_put_unlocked(&obj->base);
> +

The pattern in the other GEM drivers is not to have these extra
newlines.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

>         if (ret)
> -               goto err;
> +               return ERR_PTR(ret);
>  
>         return &obj->base;
> -
> -err:
> -       __vgem_gem_destroy(obj);
> -       return ERR_PTR(ret);
>  }
>  
>  static int vgem_gem_dumb_create(struct drm_file *file, struct drm_device *dev,
> -- 
> 2.21.0.rc2.261.ga7da99ff1b-goog
>
Eric Biggers Feb. 26, 2019, 9:30 p.m. UTC | #2 
On Tue, Feb 26, 2019 at 09:01:29PM +0000, Chris Wilson wrote:
> Quoting Eric Biggers (2019-02-26 20:47:26)
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > If drm_gem_handle_create() fails in vgem_gem_create(), then the
> > drm_vgem_gem_object is freed twice: once when the reference is dropped
> > by drm_gem_object_put_unlocked(), and again by __vgem_gem_destroy().
> > 
> > This was hit by syzkaller using fault injection.
> > 
> > Fix it by skipping the second free.
> > 
> > Reported-by: syzbot+e73f2fb5ed5a5df36d33@syzkaller.appspotmail.com
> > Fixes: 5ba6c9ff961a ("drm/vgem: Fix mmaping")
> 
> That's the wrong fixes line, it's
> Fixes: af33a9190d02 ("drm/vgem: Enable dmabuf import interfaces")
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> 
> Sadly I reviewed it so I'm still culpable, but the fix is correct as the
> put purposely frees it on error.
> 

You're right; I misread the code at that commit.
I'll resend with the correct tags.

> > Cc: stable@vger.kernel.org
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> 
> > ---
> >  drivers/gpu/drm/vgem/vgem_drv.c | 8 +++-----
> >  1 file changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> > index 5930facd6d2d8..70646d9da1596 100644
> > --- a/drivers/gpu/drm/vgem/vgem_drv.c
> > +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> > @@ -189,15 +189,13 @@ static struct drm_gem_object *vgem_gem_create(struct drm_device *dev,
> >                 return ERR_CAST(obj);
> >  
> >         ret = drm_gem_handle_create(file, &obj->base, handle);
> > +
> >         drm_gem_object_put_unlocked(&obj->base);
> > +
> 
> The pattern in the other GEM drivers is not to have these extra
> newlines.
> 
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> 
> >         if (ret)
> > -               goto err;
> > +               return ERR_PTR(ret);
> >  
> >         return &obj->base;
> > -
> > -err:
> > -       __vgem_gem_destroy(obj);
> > -       return ERR_PTR(ret);
> >  }
> >  
> >  static int vgem_gem_dumb_create(struct drm_file *file, struct drm_device *dev,
> > -- 
> > 2.21.0.rc2.261.ga7da99ff1b-goog
> >
Sasha Levin Feb. 27, 2019, 1:23 p.m. UTC | #3 
Hi,

[This is an automated email]

This commit has been processed because it contains a "Fixes:" tag,
fixing commit: 5ba6c9ff961a drm/vgem: Fix mmaping.

The bot has tested the following trees: v4.20.12, v4.19.25, v4.14.103, v4.9.160.

v4.20.12: Build OK!
v4.19.25: Build OK!
v4.14.103: Build OK!
v4.9.160: Failed to apply! Possible dependencies:
    024b6a63138c ("gpu: drm: gma500: Use vma_pages()")
    1a29d85eb0f1 ("mm: use vmf->address instead of of vmf->virtual_address")
    82b0f8c39a38 ("mm: join struct fault_env and vm_fault")
    953c66c2b22a ("mm: THP page cache support for ppc64")
    af33a9190d02 ("drm/vgem: Enable dmabuf import interfaces")
    c54fd47aa5b8 ("drm/vgem: switch to drm_*_get(), drm_*_put() helpers")
    fd60775aea80 ("mm, thp: avoid unlikely branches for split_huge_pmd")


How should we proceed with this patch?

--
Thanks,
Sasha
diff mbox series

Patch

diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
index 5930facd6d2d8..70646d9da1596 100644
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -189,15 +189,13 @@  static struct drm_gem_object *vgem_gem_create(struct drm_device *dev,
 		return ERR_CAST(obj);
 
 	ret = drm_gem_handle_create(file, &obj->base, handle);
+
 	drm_gem_object_put_unlocked(&obj->base);
+
 	if (ret)
-		goto err;
+		return ERR_PTR(ret);
 
 	return &obj->base;
-
-err:
-	__vgem_gem_destroy(obj);
-	return ERR_PTR(ret);
 }
 
 static int vgem_gem_dumb_create(struct drm_file *file, struct drm_device *dev,