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[81.185.165.206]) by smtp.gmail.com with ESMTPSA id x5sm17823427wrg.69.2019.09.04.03.19.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Sep 2019 03:19:52 -0700 (PDT) Subject: Re: [PATCH net] net: sonic: remove dev_kfree_skb before return NETDEV_TX_BUSY To: Mao Wenan , tsbogend@alpha.franken.de, davem@davemloft.net Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org References: <20190904094211.117454-1-maowenan@huawei.com> From: Eric Dumazet Message-ID: Date: Wed, 4 Sep 2019 12:19:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190904094211.117454-1-maowenan@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 9/4/19 11:42 AM, Mao Wenan wrote: > When dma_map_single is failed to map buffer, skb can't be freed > before sonic driver return to stack with NETDEV_TX_BUSY, because > this skb may be requeued to qdisc, it might trigger use-after-free. > > Fixes: d9fb9f384292 ("*sonic/natsemi/ns83829: Move the National Semi-conductor drivers") > Signed-off-by: Mao Wenan > --- > drivers/net/ethernet/natsemi/sonic.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/drivers/net/ethernet/natsemi/sonic.c b/drivers/net/ethernet/natsemi/sonic.c > index d0a01e8f000a..248a8f22a33b 100644 > --- a/drivers/net/ethernet/natsemi/sonic.c > +++ b/drivers/net/ethernet/natsemi/sonic.c > @@ -233,7 +233,6 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev) > laddr = dma_map_single(lp->device, skb->data, length, DMA_TO_DEVICE); > if (!laddr) { > printk(KERN_ERR "%s: failed to map tx DMA buffer.\n", dev->name); > - dev_kfree_skb(skb); > return NETDEV_TX_BUSY; > } > > That is the wrong way to fix this bug. What guarantee do we have that the mapping operation will succeed next time we attempt the transmit (and the dma_map_single() operation) ? NETDEV_TX_BUSY is very dangerous, this might trigger an infinite loop. I would rather leave the dev_kfree_skb(skb), and return NETDEV_TX_OK Also the printk(KERN_ERR ...) should be replaced by pr_err_ratelimited(...) NETDEV_TX_BUSY really should only be used by drivers that call netif_tx_stop_queue() at the wrong moment.