From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f47.google.com (mail-wm1-f47.google.com [209.85.128.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 15B65359A90 for ; Tue, 6 Oct 2026 12:08:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791288523; cv=none; b=sGJfHupPSAylihCWJOA67y0kWCII1mZz/5sk/tcTqNVtoo27lbaRuTwlbShGcmmLwljh0HdN8YOipVokvEH/eoYdgQ4Fyf9D31Gl+4Wa+SBJCg7b57YkCLHOxNnxGqYzOKpW9uBLS8uaICran9ZlQIwGvEhJqP0d9jdBTVDKqTM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791288523; c=relaxed/simple; bh=3S1ODil890UZ3AlrML5DJqdlWzXaY3QURyOr/71QQd0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=OFN7K+6rYAj4zIbFj5DL7K8vZWzJpMnNvQb1hzMpHfye9yPxkximturwYQBkfjWkDjYGDTTiITyHKUE8TCTy9KklvT8hD6P2DogRvPggZmSRt9tWANI0sJiQxKZiTyZRXpYUVgdaLQi5SDutqCq0ZS3erYE6xb0VHJlqjcII0as= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=GSfd4XNq; arc=none smtp.client-ip=209.85.128.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GSfd4XNq" Received: by mail-wm1-f47.google.com with SMTP id 5b1f17b1804b1-4a17b4c6133so5544455e9.1 for ; Tue, 06 Oct 2026 05:08:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1791288520; x=1791893320; darn=vger.kernel.org; h=content-transfer-encoding:content-type:mime-version:message-id:date :subject:cc:to:from:from:to:cc:subject:date:message-id:reply-to :content-type; bh=je8cwPxHIss8SyidCLgD3aHQ+Cf/hSNGW28mAiVpfKY=; b=GSfd4XNqNyjiONUlHTtXWbR1XqwM/jOVdBPat1RoYDkLSbj5l0AkgO1g0hO7Rn6Ol/ +xqOi4efd+/lxHBY8ijfSbbw1vE+pMSduBAoJu0g8DYPbuFBCVUBrnDoDtcB9ToQIngX S5EpRyQO/XXU0kyJN9lfbycQM1KStiigT/XA2KyKX9J4lZsEBcmV9kB0e1s+Umst8i9q J6m4S2tNidQ3ko5qdOsJL16FYy16K4g1Fx7+GAvC5bJa60kEoclYCGE6uwrpUl2M8PCj AHNpR71azcHXfFw3kRZ91zdrddVtq7TOi/gyPawoMi14GT9H9G0LEC4cQT2cQvgJLlwM G7CQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791288520; x=1791893320; h=content-transfer-encoding:content-type:mime-version:message-id:date :subject:cc:to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to:content-type; bh=je8cwPxHIss8SyidCLgD3aHQ+Cf/hSNGW28mAiVpfKY=; b=Sbn61QdBr4qsqshwOqk+OiS9mTNhyHbVlKpwh3pGCiX86bBJuNVgFWI0K4Hhzmulwh Je/2NefMNdZAla7+mvJ8oHTdwGipaZifkMDv384u/71bpxNzprTPUsE7BYcsqLzJngQs Rs0oeZ2XS3fkkwV6+nxyWqIB4GmkP5bqW9tiVLLgV9Sq6c22EiMatU98bmP3xaPybZnj lvNL6FpR1zT9D8g6RV1ps1F6xnV6SY7GyWNcTCQR4wk6/K5BCsVMsl1+ubo+SExq6H5H WmAgE9at9OhYjRYt9ZkkWjcOlAfFv8R+lAVdWWS5Jg79ZliXL4XoR8eZTf3yo/wBTjkS 0Udw== X-Gm-Message-State: AFuF++nxgHwKlc6peUyDi0IHpZraRHFby0zVa+MNH5q5dKZ4K/OzmfIE bWVCBDIfeK8xoZ27ia0yZzB4LSxRjel+zClX5HNVn7raG43uZBk+LbOxt/LTqqWi X-Gm-Gg: AYBFou3EFx5A9Srr6TSyOqyQfjdwsDfyf/czVV8mEv4iVSTlr4f12n79jiMhgHyxWfO dKJxQPgkyEO90kyrvGH+J/368iwfJn1Q6r4RJEfXr0UIX/7nzXVoNt438Qmt3lLcDmVqQ+RMHwn jYqDaYhgCAvPCIqQt0iPVPa6SIHfo9BZaYO49qfbiga0kACK7UTq6fdfloqiAL1fJSf8Ev9ORXw SrmizIXeiSM7ODS/4L7Otx+xoKSLbiJ7q0pB00tJkR9vAV2Lml4gdc8nA7eJCeSY+aR9yfq/ZSd if/tKwAjRxEGnnjaMKA9g8jtk1wlUiKMZpe3ZMpumWLx/Sw/Cw4Kf/eDG+ZMXpRpzTDUEbV9OFz zTTglnsTCwN1BYgxmkg1j6S7qn3ejTYUBlLcWnrTBTgjFn7LxowwdANqfGUCk8ZLs9zSZrcVlqf k6+5M8fm/u+gLnL1F6sZrSMScK12tzuFtl2pF52ZNwxHRdBDFfhgsLRzhaqfx0zySczQ2X X-Received: by 2002:a05:600c:c16f:b0:4a1:65d2:7912 with SMTP id 5b1f17b1804b1-4a17b527aebmr19859395e9.8.1791288519978; Tue, 06 Oct 2026 05:08:39 -0700 (PDT) Received: from metepc ([46.197.185.71]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a0394c937csm246918505e9.1.2026.10.06.05.08.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Oct 2026 05:08:39 -0700 (PDT) From: =?UTF-8?q?=C3=96mer=20Mete=20Kaya?= To: netdev@vger.kernel.org Cc: oneukum@suse.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, =?UTF-8?q?=C3=96mer=20Mete=20Kaya?= Subject: [PATCH net v2] usbnet: fix EVENT_RX_PAUSED race in usbnet_skb_return() Date: Tue, 6 Oct 2026 15:07:04 +0300 Message-ID: <20261006120825.342164-1-omermetekaya0@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit usbnet_resume_rx() disables local BHs before clearing EVENT_RX_PAUSED, but this does not synchronize with usbnet_skb_return() running on another CPU. On SMP, usbnet_skb_return() on CPU0 can pass the test_bit() check while CPU1 runs usbnet_resume_rx(), clears the flag and drains the queue, leaving the skb stranded in rxq_pause until the next MTU change or device stop. Fix with a double-check pattern: move clear_bit() in usbnet_resume_rx() under rxq_pause.lock; in usbnet_skb_return() take the lock and recheck the flag only on the slow path (unlikely paused), keeping the normal RX fast path lock-free. Fixes: 43daa96b166c ("usbnet: Stop RX Q on MTU change") Signed-off-by: Ömer Mete Kaya --- v2: Squash usbnet_resume_rx() fix into same patch; previous version only changed usbnet_skb_return() and was missing the clear_bit() change. drivers/net/usb/usbnet.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c index 84f97f448b2d..5eba2cef8bac 100644 --- a/drivers/net/usb/usbnet.c +++ b/drivers/net/usb/usbnet.c @@ -329,9 +329,14 @@ void usbnet_skb_return(struct usbnet *dev, struct sk_buff *skb) unsigned long flags; int status; - if (test_bit(EVENT_RX_PAUSED, &dev->flags)) { - skb_queue_tail(&dev->rxq_pause, skb); - return; + if (unlikely(test_bit(EVENT_RX_PAUSED, &dev->flags))) { + spin_lock_bh(&dev->rxq_pause.lock); + if (test_bit(EVENT_RX_PAUSED, &dev->flags)) { + __skb_queue_tail(&dev->rxq_pause, skb); + spin_unlock_bh(&dev->rxq_pause.lock); + return; + } + spin_unlock_bh(&dev->rxq_pause.lock); } /* only update if unset to allow minidriver rx_fixup override */ @@ -701,8 +706,9 @@ void usbnet_resume_rx(struct usbnet *dev) struct sk_buff *skb; int num = 0; - local_bh_disable(); + spin_lock_bh(&dev->rxq_pause.lock); clear_bit(EVENT_RX_PAUSED, &dev->flags); + spin_unlock_bh(&dev->rxq_pause.lock); while ((skb = skb_dequeue(&dev->rxq_pause)) != NULL) { usbnet_skb_return(dev, skb); @@ -710,7 +716,6 @@ void usbnet_resume_rx(struct usbnet *dev) } queue_work(system_bh_wq, &dev->bh_work); - local_bh_enable(); netif_dbg(dev, rx_status, dev->net, "paused rx queue disabled, %d skbs requeued\n", num); -- 2.55.0