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Fri, 20 Aug 2021 03:03:37 -0700 (PDT) From: Desmond Cheong Zhi Xi 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 Subject: [PATCH v4 1/5] drm: fix null ptr dereference in drm_master_release Date: Fri, 20 Aug 2021 18:02:47 +0800 Message-Id: <20210820100251.448346-2-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210820100251.448346-1-desmondcheongzx@gmail.com> References: <20210820100251.448346-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 Cc: intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, Desmond Cheong Zhi Xi , linux-kernel-mentees@lists.linuxfoundation.org, linux-media@vger.kernel.org X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" 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 --- 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 _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees