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Wed, 09 Jan 2019 03:23:09 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x093N9ek012544 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 9 Jan 2019 03:23:09 GMT Received: from abhmp0019.oracle.com (abhmp0019.oracle.com [141.146.116.25]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x093N8oP002607; Wed, 9 Jan 2019 03:23:08 GMT Received: from [10.182.69.170] (/10.182.69.170) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 08 Jan 2019 19:23:08 -0800 Subject: Re: [PATCH] net: nvidia: forcedeth: Fix two possible concurrency use-after-free bugs To: Jia-Ju Bai , davem@davemloft.net, keescook@chromium.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20190108124518.21986-1-baijiaju1990@gmail.com> <27392ae0-2c0f-f099-05d8-f9cdbfbd313e@oracle.com> <54c2efce-18ac-46d4-7fb5-8510699b528e@gmail.com> From: Yanjun Zhu Organization: Oracle Corporation Message-ID: Date: Wed, 9 Jan 2019 11:24:47 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <54c2efce-18ac-46d4-7fb5-8510699b528e@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9130 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=659 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901090025 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/1/9 11:20, Jia-Ju Bai wrote: > > > On 2019/1/9 10:35, Yanjun Zhu wrote: >> >> On 2019/1/9 10:03, Jia-Ju Bai wrote: >>> >>> >>> On 2019/1/9 9:24, Yanjun Zhu wrote: >>>> >>>> On 2019/1/8 20:57, Jia-Ju Bai wrote: >>>>> >>>>> >>>>> On 2019/1/8 20:54, Zhu Yanjun wrote: >>>>>> >>>>>> 在 2019/1/8 20:45, Jia-Ju Bai 写道: >>>>>>> In drivers/net/ethernet/nvidia/forcedeth.c, the functions >>>>>>> nv_start_xmit() and nv_start_xmit_optimized() can be concurrently >>>>>>> executed with nv_poll_controller(). >>>>>>> >>>>>>> nv_start_xmit >>>>>>>    line 2321: prev_tx_ctx->skb = skb; >>>>>>> >>>>>>> nv_start_xmit_optimized >>>>>>>    line 2479: prev_tx_ctx->skb = skb; >>>>>>> >>>>>>> nv_poll_controller >>>>>>>    nv_do_nic_poll >>>>>>>      line 4134: spin_lock(&np->lock); >>>>>>>      nv_drain_rxtx >>>>>>>        nv_drain_tx >>>>>>>          nv_release_txskb >>>>>>>            line 2004: dev_kfree_skb_any(tx_skb->skb); >>>>>>> >>>>>>> Thus, two possible concurrency use-after-free bugs may occur. >>>>>>> >>>>>>> To fix these possible bugs, >>>>>> >>>>>> >>>>>> Does this really occur? Can you reproduce this ? >>>>> >>>>> This bug is not found by the real execution. >>>>> It is found by a static tool written by myself, and then I check >>>>> it by manual code review. >>>> >>>> Before "line 2004: dev_kfree_skb_any(tx_skb->skb); ", >>>> >>>> " >>>> >>>>                 nv_disable_irq(dev); >>>>                 nv_napi_disable(dev); >>>>                 netif_tx_lock_bh(dev); >>>>                 netif_addr_lock(dev); >>>>                 spin_lock(&np->lock); >>>>                 /* stop engines */ >>>>                 nv_stop_rxtx(dev);   <---this stop rxtx >>>>                 nv_txrx_reset(dev); >>>> " >>>> >>>> In this case, does nv_start_xmit or nv_start_xmit_optimized still >>>> work well? >>>> >>> >>> nv_stop_rxtx() calls nv_stop_tx(dev). >>> >>> static void nv_stop_tx(struct net_device *dev) >>> { >>>     struct fe_priv *np = netdev_priv(dev); >>>     u8 __iomem *base = get_hwbase(dev); >>>     u32 tx_ctrl = readl(base + NvRegTransmitterControl); >>> >>>     if (!np->mac_in_use) >>>         tx_ctrl &= ~NVREG_XMITCTL_START; >>>     else >>>         tx_ctrl |= NVREG_XMITCTL_TX_PATH_EN; >>>     writel(tx_ctrl, base + NvRegTransmitterControl); >>>     if (reg_delay(dev, NvRegTransmitterStatus, NVREG_XMITSTAT_BUSY, 0, >>>               NV_TXSTOP_DELAY1, NV_TXSTOP_DELAY1MAX)) >>>         netdev_info(dev, "%s: TransmitterStatus remained busy\n", >>>                 __func__); >>> >>>     udelay(NV_TXSTOP_DELAY2); >>>     if (!np->mac_in_use) >>>         writel(readl(base + NvRegTransmitPoll) & >>> NVREG_TRANSMITPOLL_MAC_ADDR_REV, >>>                base + NvRegTransmitPoll); >>> } >>> >>> nv_stop_tx() seems to only write registers to stop transmitting for >>> hardware. >>> But it does not wait until nv_start_xmit() and >>> nv_start_xmit_optimized() finish execution. >> There are 3 modes in forcedeth NIC. >> In throughput mode (0), every tx & rx packet will generate an interrupt. >> In CPU mode (1), interrupts are controlled by a timer. >> In dynamic mode (2), the mode toggles between throughput and CPU mode >> based on network load. >> >> From the source code, >> >> "np->recover_error = 1;" is related with CPU mode. >> >> nv_start_xmit or nv_start_xmit_optimized seems related with >> ghroughput mode. >> >> In static void nv_do_nic_poll(struct timer_list *t), >> when  if (np->recover_error), line 2004: >> dev_kfree_skb_any(tx_skb->skb); will run. >> >> When "np->recover_error=1", do you think nv_start_xmit or >> nv_start_xmit_optimized will be called? > > Sorry, I do not know about these modes... > But I still think nv_start_xmit() or nv_start_xmit_optimized() can be > called here, in no matter which mode :) :-P If you have forcedeth NIC, you can make tests with it.:-) > > > Best wishes, > Jia-Ju Bai >