linux-kernel - [PATCH] drm/vmwgfx:fix refcount leak in vmw_kms_fb

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Message-Id: <20211223021342.3650-1-xiongx18@fudan.edu.cn>
Date:   Thu, 23 Dec 2021 10:13:42 +0800
From:   Xin Xiong <xiongx18@...an.edu.cn>
To:     VMware Graphics <linux-graphics-maintainer@...are.com>,
        Zack Rusin <zackr@...are.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, Xin Xiong <xiongx18@...an.edu.cn>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH] drm/vmwgfx:fix refcount leak in vmw_kms_fb_create()

This issue happens in one error path of vmw_kms_fb_create(). The
function forgets to decrement the refcount of a ttm_base_object obj,
which is increased by vmw_user_lookup_handle() earlier, when
vmw_user_lookup_handle() returns 0 but vfb is not yet created. This
may incur reference count leak.

Fix it by decrement reference count in that error path instead of
assigning the obj to vfb->user_obj.

Signed-off-by: Xin Xiong <xiongx18@...an.edu.cn>
Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index 74fa41909..453fa714f 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -1426,7 +1426,7 @@ static struct drm_framebuffer *vmw_kms_fb_create(struct drm_device *dev,
 	if (surface)
 		vmw_surface_unreference(&surface);
 
-	if (ret) {
+	if (ret || !vfb) {
 		DRM_ERROR("failed to create vmw_framebuffer: %i\n", ret);
 		ttm_base_object_unref(&user_obj);
 		return ERR_PTR(ret);
-- 
2.25.1