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Fri, 09 Oct 2026 08:48:51 -0700 (PDT) Received: from [192.168.18.21] ([46.197.185.71]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a18bf2343asm120627275e9.9.2026.10.09.08.48.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Oct 2026 08:48:51 -0700 (PDT) Message-ID: Date: Fri, 9 Oct 2026 18:48:50 +0300 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v3] usbnet: fix EVENT_RX_PAUSED race in usbnet_skb_return() To: sashiko-reviews@lists.linux.dev Cc: linux-usb@vger.kernel.org References: <20261007220311.113827-1-omermetekaya0@gmail.com> Content-Language: en-US From: =?UTF-8?Q?=C3=96mer_Mete_Kaya?= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 10/9/26 01:03, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [Medium] net: out-of-order packet delivery during RX resume > -- > > commit 7148b0b2b0b945f31b2120d7f4cbc269acf91635 > Author: Ömer Mete Kaya > > usbnet: fix EVENT_RX_PAUSED race in usbnet_skb_return() > > This commit addresses a race condition in usbnet_skb_return() by protecting > the EVENT_RX_PAUSED flag check and enqueue operations with a double-check > pattern under the rxq_pause lock. It also protects the clear_bit() operation > in usbnet_resume_rx() under the same lock. > >> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c >> index a19ecf718f36a..d1ec3ba1e10e6 100644 >> --- a/drivers/net/usb/usbnet.c >> +++ b/drivers/net/usb/usbnet.c > [ ... ] >> @@ -700,15 +705,16 @@ void usbnet_resume_rx(struct usbnet *dev) >> int num = 0; >> >> local_bh_disable(); >> + spin_lock(&dev->rxq_pause.lock); >> clear_bit(EVENT_RX_PAUSED, &dev->flags); >> - >> + spin_unlock(&dev->rxq_pause.lock); > > [Severity: Medium] > If a new packet arrives concurrently on another CPU via usbnet_skb_return(), > could it observe EVENT_RX_PAUSED as false here? > > If so, it would bypass the pause queue and immediately deliver the new SKB > to the network stack via netif_rx(). > >> while ((skb = skb_dequeue(&dev->rxq_pause)) != NULL) { >> usbnet_skb_return(dev, skb); >> num++; >> } > > This seems like it would cause the newly arrived packet to be delivered before > the older packets in the rxq_pause queue are fully drained by this while loop, > leading to out-of-order delivery which can degrade TCP performance. > The out-of-order delivery window between clear_bit() and the drain loop is a pre-existing issue in the original code, not introduced by this patch.