From patchwork Wed Nov 29 21:25:20 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Doug Anderson X-Patchwork-Id: 13473451 X-Patchwork-Delegate: kuba@kernel.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="ZPvbimEB" Received: from mail-pg1-x532.google.com (mail-pg1-x532.google.com [IPv6:2607:f8b0:4864:20::532]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 501C410C0 for ; Wed, 29 Nov 2023 13:26:22 -0800 (PST) Received: by mail-pg1-x532.google.com with SMTP id 41be03b00d2f7-5c210e34088so207530a12.2 for ; Wed, 29 Nov 2023 13:26:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1701293182; x=1701897982; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=XNCUzlT66xSSzQeRG+3/Vjdg0+tkFMt3clYOj0yBxCw=; b=ZPvbimEBh8xSzwTEtOWWe8MrLkwmup8mXmlIf/LDDw3wIQZtQKqvu4z4cZG3icQ545 xazyz2ORF4ObT7bM6rXCBKc1U1zseYGa29BjCouutJ6/+yohq4zgKUds36bgl4iOPy6B 4+ds8kxiTIR0fxRSi5Pz+t2uldV7nCBzVbQk4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701293182; x=1701897982; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=XNCUzlT66xSSzQeRG+3/Vjdg0+tkFMt3clYOj0yBxCw=; b=X7rWE8iiPHzHMFMkX/4rV38oACat8kwfY07GGTgN2IXyIW34eHZYa9dGp61ZYOoewb KVH5whxWpoBAcfPjiBysmI68T6DR+vFEtEjyvJLkYx3GJwxYjfJH3eZthmThO90ZScou +g+CSKAXsmWf3SuJ2njlGldevT8Sq125TzT7xvq3wKbOpvny0oy3xGqsQQQLMf9QejTU XQBRPlmKmqXPclK7y8j3jOpnGM8kbcRC/hpxLOTT6xFlgxU6UO/BOzcm+UcCJHX/ySn0 AbTMSfoiMVAmLpzyLpqLJbbsSiJV4EImGfhRwVT4DkE4iZzxRgp+qJiviEh6Numx5k39 dLBQ== X-Gm-Message-State: AOJu0Ywaw34sw5XHxVRbs93SIjmsGVfql5TzuwzmKFTEhp2QNJlmlLGV M8RciYHgPIXqjuMJP4svkvUi6A== X-Google-Smtp-Source: AGHT+IGOwv+JMe9LhytdON3udR8lCNrEUEhKRkteEYEJXfm1i3wfjX3UCluoIHcPnUFu32ZmHv+K/A== X-Received: by 2002:a05:6a20:244b:b0:18c:fa:17f7 with SMTP id t11-20020a056a20244b00b0018c00fa17f7mr24241206pzc.46.1701293181673; Wed, 29 Nov 2023 13:26:21 -0800 (PST) Received: from tictac2.mtv.corp.google.com ([2620:15c:9d:2:dcf:15e4:5f50:e692]) by smtp.gmail.com with ESMTPSA id t22-20020a634616000000b005c215baacc1sm11816336pga.70.2023.11.29.13.26.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Nov 2023 13:26:21 -0800 (PST) From: Douglas Anderson To: Jakub Kicinski , Hayes Wang , "David S . Miller" Cc: linux-usb@vger.kernel.org, Grant Grundler , Laura Nao , Edward Hill , Alan Stern , Simon Horman , Douglas Anderson , =?utf-8?q?Bj=C3=B8rn_Mork?= , Eric Dumazet , Paolo Abeni , linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH net v3 1/5] r8152: Hold the rtnl_lock for all of reset Date: Wed, 29 Nov 2023 13:25:20 -0800 Message-ID: <20231129132521.net.v3.1.I77097aa9ec01aeca1b3c75fde4ba5007a17fdf76@changeid> X-Mailer: git-send-email 2.43.0.rc1.413.gea7ed67945-goog Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org As of commit d9962b0d4202 ("r8152: Block future register access if register access fails") there is a race condition that can happen between the USB device reset thread and napi_enable() (not) getting called during rtl8152_open(). Specifically: * While rtl8152_open() is running we get a register access error that's _not_ -ENODEV and queue up a USB reset. * rtl8152_open() exits before calling napi_enable() due to any reason (including usb_submit_urb() returning an error). In that case: * Since the USB reset is perform in a separate thread asynchronously, it can run at anytime USB device lock is not held - even before rtl8152_open() has exited with an error and caused __dev_open() to clear the __LINK_STATE_START bit. * The rtl8152_pre_reset() will notice that the netif_running() returns true (since __LINK_STATE_START wasn't cleared) so it won't exit early. * rtl8152_pre_reset() will then hang in napi_disable() because napi_enable() was never called. We can fix the race by making sure that the r8152 reset routines don't run at the same time as we're opening the device. Specifically we need the reset routines in their entirety rely on the return value of netif_running(). The only way to reliably depend on that is for them to hold the rntl_lock() mutex for the duration of reset. Grabbing the rntl_lock() mutex for the duration of reset seems like a long time, but reset is not expected to be common and the rtnl_lock() mutex is already held for long durations since the core grabs it around the open/close calls. Fixes: d9962b0d4202 ("r8152: Block future register access if register access fails") Reviewed-by: Grant Grundler Signed-off-by: Douglas Anderson --- In response to v1 Paolo questioned the wisdom of grabbing the rtnl_lock in the USB pre_reset() and releasing it in the USB post_reset() [1]. While his concern is a legitimate one because this looks a bit fragile, I'm still of the belief that the current patch is the best solution. This patch has been tested with lockdep and I saw no splats about it. I've also read through the usb core code twice and I don't see any way that post_reset() won't be called if pre_reset() was called, assuming that the pre_reset() doesn't return an error (we never return an error from pre_reset()). If folks have some example of something that's broken by the current rtnl_lock strategy used by this patch (or if folks feel very strongly that it needs to be changed) then I can spin another version. ...but as per my reply to Paolo [2] I think that does have some minor downsides. [1] https://lore.kernel.org/r/f8c1979e2c71d871998aec0126dd87adb5e76cce.camel@redhat.com [2] https://lore.kernel.org/r/CAD=FV=VqZq33eLiFPNiZCJmewQ1hxECmUnwbjVbvdJiDkQMAJA@mail.gmail.com (no changes since v2) Changes in v2: - Added "after the cut" notes about rtnl lock strategy. drivers/net/usb/r8152.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c index 2c5c1e91ded6..d6edf0254599 100644 --- a/drivers/net/usb/r8152.c +++ b/drivers/net/usb/r8152.c @@ -8397,6 +8397,8 @@ static int rtl8152_pre_reset(struct usb_interface *intf) struct r8152 *tp = usb_get_intfdata(intf); struct net_device *netdev; + rtnl_lock(); + if (!tp || !test_bit(PROBED_WITH_NO_ERRORS, &tp->flags)) return 0; @@ -8428,20 +8430,17 @@ static int rtl8152_post_reset(struct usb_interface *intf) struct sockaddr sa; if (!tp || !test_bit(PROBED_WITH_NO_ERRORS, &tp->flags)) - return 0; + goto exit; rtl_set_accessible(tp); /* reset the MAC address in case of policy change */ - if (determine_ethernet_addr(tp, &sa) >= 0) { - rtnl_lock(); + if (determine_ethernet_addr(tp, &sa) >= 0) dev_set_mac_address (tp->netdev, &sa, NULL); - rtnl_unlock(); - } netdev = tp->netdev; if (!netif_running(netdev)) - return 0; + goto exit; set_bit(WORK_ENABLE, &tp->flags); if (netif_carrier_ok(netdev)) { @@ -8460,6 +8459,8 @@ static int rtl8152_post_reset(struct usb_interface *intf) if (!list_empty(&tp->rx_done)) napi_schedule(&tp->napi); +exit: + rtnl_unlock(); return 0; }