Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933266AbcK3Jyy (ORCPT ); Wed, 30 Nov 2016 04:54:54 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:33056 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964803AbcK3JcM (ORCPT ); Wed, 30 Nov 2016 04:32:12 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Takashi Iwai , Mauro Carvalho Chehab Subject: [PATCH 4.8 30/37] xc2028: Fix use-after-free bug properly Date: Wed, 30 Nov 2016 10:30:07 +0100 Message-Id: <20161130092731.113714372@linuxfoundation.org> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161130092729.623248210@linuxfoundation.org> References: <20161130092729.623248210@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3751 Lines: 129 4.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit 22a1e7783e173ab3d86018eb590107d68df46c11 upstream. The commit 8dfbcc4351a0 ("[media] xc2028: avoid use after free") tried to address the reported use-after-free by clearing the reference. However, it's clearing the wrong pointer; it sets NULL to priv->ctrl.fname, but it's anyway overwritten by the next line memcpy(&priv->ctrl, p, sizeof(priv->ctrl)). OTOH, the actual code accessing the freed string is the strcmp() call with priv->fname: if (!firmware_name[0] && p->fname && priv->fname && strcmp(p->fname, priv->fname)) free_firmware(priv); where priv->fname points to the previous file name, and this was already freed by kfree(). For fixing the bug properly, this patch does the following: - Keep the copy of firmware file name in only priv->fname, priv->ctrl.fname isn't changed; - The allocation is done only when the firmware gets loaded; - The kfree() is called in free_firmware() commonly Fixes: commit 8dfbcc4351a0 ('[media] xc2028: avoid use after free') Signed-off-by: Takashi Iwai Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Greg Kroah-Hartman --- drivers/media/tuners/tuner-xc2028.c | 37 +++++++++++++++--------------------- 1 file changed, 16 insertions(+), 21 deletions(-) --- a/drivers/media/tuners/tuner-xc2028.c +++ b/drivers/media/tuners/tuner-xc2028.c @@ -281,6 +281,14 @@ static void free_firmware(struct xc2028_ int i; tuner_dbg("%s called\n", __func__); + /* free allocated f/w string */ + if (priv->fname != firmware_name) + kfree(priv->fname); + priv->fname = NULL; + + priv->state = XC2028_NO_FIRMWARE; + memset(&priv->cur_fw, 0, sizeof(priv->cur_fw)); + if (!priv->firm) return; @@ -291,9 +299,6 @@ static void free_firmware(struct xc2028_ priv->firm = NULL; priv->firm_size = 0; - priv->state = XC2028_NO_FIRMWARE; - - memset(&priv->cur_fw, 0, sizeof(priv->cur_fw)); } static int load_all_firmwares(struct dvb_frontend *fe, @@ -884,9 +889,8 @@ read_not_reliable: return 0; fail: - priv->state = XC2028_NO_FIRMWARE; + free_firmware(priv); - memset(&priv->cur_fw, 0, sizeof(priv->cur_fw)); if (retry_count < 8) { msleep(50); retry_count++; @@ -1332,11 +1336,8 @@ static int xc2028_dvb_release(struct dvb mutex_lock(&xc2028_list_mutex); /* only perform final cleanup if this is the last instance */ - if (hybrid_tuner_report_instance_count(priv) == 1) { + if (hybrid_tuner_report_instance_count(priv) == 1) free_firmware(priv); - kfree(priv->ctrl.fname); - priv->ctrl.fname = NULL; - } if (priv) hybrid_tuner_release_state(priv); @@ -1399,19 +1400,8 @@ static int xc2028_set_config(struct dvb_ /* * Copy the config data. - * For the firmware name, keep a local copy of the string, - * in order to avoid troubles during device release. */ - kfree(priv->ctrl.fname); - priv->ctrl.fname = NULL; memcpy(&priv->ctrl, p, sizeof(priv->ctrl)); - if (p->fname) { - priv->ctrl.fname = kstrdup(p->fname, GFP_KERNEL); - if (priv->ctrl.fname == NULL) { - rc = -ENOMEM; - goto unlock; - } - } /* * If firmware name changed, frees firmware. As free_firmware will @@ -1426,10 +1416,15 @@ static int xc2028_set_config(struct dvb_ if (priv->state == XC2028_NO_FIRMWARE) { if (!firmware_name[0]) - priv->fname = priv->ctrl.fname; + priv->fname = kstrdup(p->fname, GFP_KERNEL); else priv->fname = firmware_name; + if (!priv->fname) { + rc = -ENOMEM; + goto unlock; + } + rc = request_firmware_nowait(THIS_MODULE, 1, priv->fname, priv->i2c_props.adap->dev.parent,