From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Subject: [PATCH] drm/vgem: fix use-after-free when drm_gem_handle_create() fails Date: Tue, 26 Feb 2019 12:47:26 -0800 Message-ID: <20190226204726.92256-1-ebiggers@kernel.org> References: Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: dri-devel@lists.freedesktop.org, David Airlie , Daniel Vetter Cc: Chris Wilson , syzkaller-bugs , linux-kernel@vger.kernel.org List-Id: dri-devel@lists.freedesktop.org From: Eric Biggers 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 --- 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); + 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