From 41d931459b53e32c67a1f8838d1e6826a69ee745 Mon Sep 17 00:00:00 2001
From: Pan Bian <bianpan2016@163.com>
Date: Wed, 6 Nov 2019 15:31:07 +0800
Subject: drm/i915/gvt: fix dropping obj reference twice
Git-commit: 41d931459b53e32c67a1f8838d1e6826a69ee745
Patch-mainline: v5.4-rc8
References: bsc#1152489
The reference count of obj will be decremented twice if error occurs
in dma_buf_fd(). Additionally, attempting to read the reference count of
obj after dropping reference may lead to a use after free bug. Here, we
drop obj's reference until it is not used.
Fixes: e546e281d33d ("drm/i915/gvt: Dmabuf support for GVT-g")
Signed-off-by: Pan Bian <bianpan2016@163.com>
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/gpu/drm/i915/gvt/dmabuf.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gvt/dmabuf.c b/drivers/gpu/drm/i915/gvt/dmabuf.c
index 13044c027f27..4bfaefdf548d 100644
--- a/drivers/gpu/drm/i915/gvt/dmabuf.c
+++ b/drivers/gpu/drm/i915/gvt/dmabuf.c
@@ -498,8 +498,6 @@ int intel_vgpu_get_dmabuf(struct intel_vgpu *vgpu, unsigned int dmabuf_id)
goto out_free_gem;
}
- i915_gem_object_put(obj);
-
ret = dma_buf_fd(dmabuf, DRM_CLOEXEC | DRM_RDWR);
if (ret < 0) {
gvt_vgpu_err("create dma-buf fd failed ret:%d\n", ret);
@@ -524,6 +522,8 @@ int intel_vgpu_get_dmabuf(struct intel_vgpu *vgpu, unsigned int dmabuf_id)
file_count(dmabuf->file),
kref_read(&obj->base.refcount));
+ i915_gem_object_put(obj);
+
return dmabuf_fd;
out_free_dmabuf:
--
2.28.0