From: Eric Biggers <ebiggers@kernel.org>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@linux.ie>,
dri-devel@lists.freedesktop.org,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/vgem: fix use-after-free when drm_gem_handle_create() fails
Date: Tue, 26 Feb 2019 13:30:54 -0800 [thread overview]
Message-ID: <20190226213053.GC218103@gmail.com> (raw)
In-Reply-To: <155121487959.17933.15702334870310780013@skylake-alporthouse-com>
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
> >
next prev parent reply other threads:[~2019-02-26 21:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <00000000000053fea105791276d8@google.com>
2018-10-29 11:51 ` KASAN: use-after-free Read in drm_gem_object_release Dmitry Vyukov
2019-02-26 20:47 ` [PATCH] drm/vgem: fix use-after-free when drm_gem_handle_create() fails Eric Biggers
2019-02-26 21:01 ` Chris Wilson
2019-02-26 21:30 ` Eric Biggers [this message]
2019-02-26 21:44 ` [PATCH v2] " Eric Biggers
2019-02-27 23:52 ` Laura Abbott
2019-03-04 23:24 ` Rodrigo Siqueira
2019-02-26 22:08 ` [PATCH] drm/vkms: " Eric Biggers
2019-02-26 22:14 ` Chris Wilson
2019-02-27 23:12 ` Rodrigo Siqueira
2019-02-28 6:41 ` Dmitry Vyukov
2019-03-04 23:23 ` Rodrigo Siqueira
2019-03-05 14:25 ` Dmitry Vyukov
2019-03-10 15:36 ` Rodrigo Siqueira
2019-02-27 13:23 ` [PATCH] drm/vgem: " Sasha Levin
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