Re: [PATCH] drm/vmwgfx: Stop accessing buffer objects which failed init

[Martin Krastev (VMware)]

From: Martin Krastev <krast...@vmware.com>

Much nicer now.
Reviewed-by: Martin Krastev <krast...@vmware.com>


Regards,
Martin

On 8.02.23 г. 20:00 ч., Zack Rusin wrote:

From: Zack Rusin <za...@vmware.com>

ttm_bo_init_reserved on failure puts the buffer object back which
causes it to be deleted, but kfree was still being called on the same
buffer in vmw_bo_create leading to a double free.

After the double free the vmw_gem_object_create_with_handle was
setting the gem function objects before checking the return status
of vmw_bo_create leading to null pointer access.

Fix the entire path by relaying on ttm_bo_init_reserved to delete the
buffer objects on failure and making sure the return status is checked
before setting the gem function objects on the buffer object.

Signed-off-by: Zack Rusin <za...@vmware.com>
Fixes: 8afa13a0583f ("drm/vmwgfx: Implement DRIVER_GEM")
Cc: <sta...@vger.kernel.org> # v5.17+
---
  drivers/gpu/drm/vmwgfx/vmwgfx_bo.c  | 4 +++-
  drivers/gpu/drm/vmwgfx/vmwgfx_gem.c | 4 ++--
  2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c 
b/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
index 63486802c8fd..43ffa5c7acbd 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
@@ -431,13 +431,15 @@ int vmw_bo_create(struct vmw_private *vmw,
                return -ENOMEM;
        }

+ /*

+        * vmw_bo_init will delete the *p_bo object if it fails
+        */
        ret = vmw_bo_init(vmw, *p_bo, params, vmw_bo_free);
        if (unlikely(ret != 0))
                goto out_error;

return ret;

  out_error:
-       kfree(*p_bo);
        *p_bo = NULL;
        return ret;
  }
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c 
b/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
index f042e22b8b59..51bd1f8c5cc4 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
@@ -127,11 +127,11 @@ int vmw_gem_object_create_with_handle(struct vmw_private 
*dev_priv,
        };

ret = vmw_bo_create(dev_priv, &params, p_vbo);

-
-       (*p_vbo)->tbo.base.funcs = &vmw_gem_object_funcs;
        if (ret != 0)
                goto out_no_bo;

+ (*p_vbo)->tbo.base.funcs = &vmw_gem_object_funcs;

+
        ret = drm_gem_handle_create(filp, &(*p_vbo)->tbo.base, handle);
        /* drop reference from allocate - handle holds it now */
        drm_gem_object_put(&(*p_vbo)->tbo.base);