Return-path: Received: from mail.ispras.ru ([83.149.199.45]:35092 "EHLO mail.ispras.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752097Ab3IBEGE (ORCPT ); Mon, 2 Sep 2013 00:06:04 -0400 Message-ID: <52240EA9.7010207@ispras.ru> (sfid-20130902_060628_272441_36F3B0DA) Date: Mon, 02 Sep 2013 07:06:01 +0300 From: Alexey Khoroshilov MIME-Version: 1.0 To: htl10@users.sourceforge.net CC: larry.finger@lwfinger.net, linville@tuxdriver.com, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, ldv-project@linuxtesting.org, Greg Kroah-Hartman Subject: Re: [PATCH] rtl8187: fix use after free on failure path in rtl8187_init_urbs() References: <1378021881.73447.YahooMailBasic@web172302.mail.ir2.yahoo.com> In-Reply-To: <1378021881.73447.YahooMailBasic@web172302.mail.ir2.yahoo.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 01.09.2013 10:51, Hin-Tak Leung wrote: > ------------------------------ > On Sat, Aug 31, 2013 22:18 BST Alexey Khoroshilov wrote: > >> In case of __dev_alloc_skb() failure rtl8187_init_urbs() >> calls usb_free_urb(entry) where 'entry' can points to urb >> allocated at the previous iteration. That means refcnt will be >> decremented incorrectly and the urb can be used after memory >> deallocation. >> >> The patch fixes the issue and implements error handling of init_urbs >> in rtl8187_start(). >> >> Found by Linux Driver Verification project (linuxtesting.org). >> >> Signed-off-by: Alexey Khoroshilov >> --- >> drivers/net/wireless/rtl818x/rtl8187/dev.c | 15 ++++++++++----- >> 1 file changed, 10 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/net/wireless/rtl818x/rtl8187/dev.c b/drivers/net/wireless/rtl818x/rtl8187/dev.c >> index f49220e..e83d53c 100644 >> --- a/drivers/net/wireless/rtl818x/rtl8187/dev.c >> +++ b/drivers/net/wireless/rtl818x/rtl8187/dev.c >> @@ -438,17 +438,16 @@ static int rtl8187_init_urbs(struct ieee80211_hw *dev) >> skb_queue_tail(&priv->rx_queue, skb); >> usb_anchor_urb(entry, &priv->anchored); >> ret = usb_submit_urb(entry, GFP_KERNEL); >> + usb_free_urb(entry); >> if (ret) { >> skb_unlink(skb, &priv->rx_queue); >> usb_unanchor_urb(entry); >> goto err; >> } >> - usb_free_urb(entry); >> } >> return ret; >> >> err: >> - usb_free_urb(entry); >> kfree_skb(skb); >> usb_kill_anchored_urbs(&priv->anchored); >> return ret; > This part looks wrong - you free_urb(entry) then unanchor_urb(entry). I do not see any problems here. usb_free_urb() just decrements refcnt of the urb. While usb_anchor_urb() and usb_unanchor_urb() increment and decrement it as well. So actual memory deallocation will happen in usb_unanchor_urb(). > >> @@ -956,8 +955,12 @@ static int rtl8187_start(struct ieee80211_hw *dev) >> (RETRY_COUNT < 8 /* short retry limit */) | >> (RETRY_COUNT < 0 /* long retry limit */) | >> (7 < 21 /* MAX TX DMA */)); >> - rtl8187_init_urbs(dev); >> - rtl8187b_init_status_urb(dev); >> + ret = rtl8187_init_urbs(dev); >> + if (ret) >> + goto rtl8187_start_exit; >> + ret = rtl8187b_init_status_urb(dev); >> + if (ret) >> + usb_kill_anchored_urbs(&priv->anchored); >> goto rtl8187_start_exit; >> } >> >> @@ -966,7 +969,9 @@ static int rtl8187_start(struct ieee80211_hw *dev) >> rtl818x_iowrite32(priv, &priv->map->MAR[0], ~0); >> rtl818x_iowrite32(priv, &priv->map->MAR[1], ~0); >> >> - rtl8187_init_urbs(dev); >> + ret = rtl8187_init_urbs(dev); >> + if (ret) >> + goto rtl8187_start_exit; >> >> reg = RTL818X_RX_CONF_ONLYERLPKT | >> RTL818X_RX_CONF_RX_AUTORESETPHY | >> -- >> 1.8.1.2 >> > >