linux-kernel - [PATCH 3/3] drm/vmwgfx: fix potential UAF in vmwgfx

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Date:   Thu, 22 Jul 2021 17:29:29 +0800
From:   Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
To:     linux-graphics-maintainer@...are.com, zackr@...are.com,
        airlied@...ux.ie, daniel@...ll.ch,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de
Cc:     Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, skhan@...uxfoundation.org,
        gregkh@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: [PATCH 3/3] drm/vmwgfx: fix potential UAF in vmwgfx_surface.c

drm_file.master should be protected by either drm_device.master_mutex
or drm_file.master_lookup_lock when being dereferenced. However,
drm_master_get is called on unprotected file_priv->master pointers in
vmw_surface_define_ioctl and vmw_gb_surface_define_internal.

This is fixed by replacing drm_master_get with drm_file_get_master.

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
index 0eba47762bed..5d53a5f9d123 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -865,7 +865,7 @@ int vmw_surface_define_ioctl(struct drm_device *dev, void *data,
 	user_srf->prime.base.shareable = false;
 	user_srf->prime.base.tfile = NULL;
 	if (drm_is_primary_client(file_priv))
-		user_srf->master = drm_master_get(file_priv->master);
+		user_srf->master = drm_file_get_master(file_priv);
 
 	/**
 	 * From this point, the generic resource management functions
@@ -1534,7 +1534,7 @@ vmw_gb_surface_define_internal(struct drm_device *dev,
 
 	user_srf = container_of(srf, struct vmw_user_surface, srf);
 	if (drm_is_primary_client(file_priv))
-		user_srf->master = drm_master_get(file_priv->master);
+		user_srf->master = drm_file_get_master(file_priv);
 
 	res = &user_srf->srf.res;
 
-- 
2.25.1