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From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
To: maarten.lankhorst@linux.intel.com, mripard@kernel.org,
	tzimmermann@suse.de, airlied@linux.ie, daniel@ffwll.ch,
	sumit.semwal@linaro.org, christian.koenig@amd.com,
	jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com,
	rodrigo.vivi@intel.com, chris@chris-wilson.co.uk,
	ville.syrjala@linux.intel.com, matthew.auld@intel.com,
	dan.carpenter@oracle.com, tvrtko.ursulin@intel.com,
	matthew.d.roper@intel.com, lucas.demarchi@intel.com,
	karthik.b.s@intel.com, jose.souza@intel.com,
	manasi.d.navare@intel.com, airlied@redhat.com,
	aditya.swarup@intel.com, andrescj@chromium.org,
	linux-graphics-maintainer@vmware.com, zackr@vmware.com
Cc: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	intel-gfx@lists.freedesktop.org, linux-media@vger.kernel.org,
	linaro-mm-sig@lists.linaro.org, skhan@linuxfoundation.org,
	gregkh@linuxfoundation.org,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: [PATCH v6 1/7] drm: fix null ptr dereference in drm_master_release
Date: Wed, 25 Aug 2021 18:24:05 +0800	[thread overview]
Message-ID: <20210825102411.1084220-2-desmondcheongzx@gmail.com> (raw)
In-Reply-To: <20210825102411.1084220-1-desmondcheongzx@gmail.com>

drm_master_release can be called on a drm_file without a master, which
results in a null ptr dereference of file_priv->master->magic_map. The
three cases are:

1. Error path in drm_open_helper
  drm_open():
    drm_open_helper():
      drm_master_open():
        drm_new_set_master(); <--- returns -ENOMEM,
                                   drm_file.master not set
      drm_file_free():
        drm_master_release(); <--- NULL ptr dereference
                                   (file_priv->master->magic_map)

2. Error path in mock_drm_getfile
  mock_drm_getfile():
    anon_inode_getfile(); <--- returns error, drm_file.master not set
    drm_file_free():
      drm_master_release(); <--- NULL ptr dereference
                                 (file_priv->master->magic_map)

3. In drm_client_close, as drm_client_open doesn't set up a master

drm_file.master is set up in drm_open_helper through the call to
drm_master_open, so we mirror it with a call to drm_master_release in
drm_close_helper, and remove drm_master_release from drm_file_free to
avoid the null ptr dereference.

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
---
 drivers/gpu/drm/drm_file.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index ed25168619fc..90b62f360da1 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -282,9 +282,6 @@ void drm_file_free(struct drm_file *file)
 
 	drm_legacy_ctxbitmap_flush(dev, file);
 
-	if (drm_is_primary_client(file))
-		drm_master_release(file);
-
 	if (dev->driver->postclose)
 		dev->driver->postclose(dev, file);
 
@@ -305,6 +302,9 @@ static void drm_close_helper(struct file *filp)
 	list_del(&file_priv->lhead);
 	mutex_unlock(&dev->filelist_mutex);
 
+	if (drm_is_primary_client(file_priv))
+		drm_master_release(file_priv);
+
 	drm_file_free(file_priv);
 }
 
-- 
2.25.1


  reply	other threads:[~2021-08-25 10:26 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-25 10:24 [PATCH v6 0/7] drm: update locking for modesetting Desmond Cheong Zhi Xi
2021-08-25 10:24 ` Desmond Cheong Zhi Xi [this message]
2021-08-25 10:24 ` [PATCH v6 2/7] drm: convert drm_device.master_mutex into a rwsem Desmond Cheong Zhi Xi
2021-08-25 10:24 ` [PATCH v6 3/7] drm: lock drm_global_mutex earlier in the ioctl handler Desmond Cheong Zhi Xi
2021-08-25 10:24 ` [PATCH v6 4/7] drm: avoid races with modesetting rights Desmond Cheong Zhi Xi
2021-08-25 10:24 ` [PATCH v6 5/7] drm: avoid circular locks in drm_mode_object_find Desmond Cheong Zhi Xi
2021-08-25 10:24 ` [PATCH v6 6/7] drm: avoid circular locks with modeset_mutex and master_rwsem Desmond Cheong Zhi Xi
2021-08-25 10:24 ` [PATCH v6 7/7] drm: remove drm_file.master_lookup_lock Desmond Cheong Zhi Xi

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