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Date: Thu, 26 Aug 2021 10:01:16 +0800 From: Desmond Cheong Zhi Xi <desmondcheongzx@...il.com> To: maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de, airlied@...ux.ie, daniel@...ll.ch, sumit.semwal@...aro.org, christian.koenig@....com, jani.nikula@...ux.intel.com, joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com, chris@...is-wilson.co.uk, ville.syrjala@...ux.intel.com, matthew.auld@...el.com, dan.carpenter@...cle.com, tvrtko.ursulin@...el.com, matthew.d.roper@...el.com, lucas.demarchi@...el.com, karthik.b.s@...el.com, jose.souza@...el.com, manasi.d.navare@...el.com, airlied@...hat.com, aditya.swarup@...el.com, andrescj@...omium.org, linux-graphics-maintainer@...are.com, zackr@...are.com Cc: Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org, linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org, skhan@...uxfoundation.org, gregkh@...uxfoundation.org, linux-kernel-mentees@...ts.linuxfoundation.org Subject: [PATCH v8 1/7] drm: fix null ptr dereference in drm_master_release 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@...il.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
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