From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f170.google.com (mail-pf1-f170.google.com [209.85.210.170]) (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 105691F63CD for ; Wed, 2 Apr 2025 23:20:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743636059; cv=none; b=cC8Zclo3VNgZrfb34Ij4a4cAES//UGHR4fUNZk0PkVI+kQGVCaQm/obHeJs1LF/UcfAH6rH0+MU/MAJmgzcK4r01DojRgt/8DBdAQS1nUahzItBca4lm7ug2g2sigydmaUzQCbzXeQMeU4RMrwpAsKI6vH1eAhpZy92xXOIQQec= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743636059; c=relaxed/simple; bh=Qp10X8LnSA1V/nxiP/4T9z0sZlVtVT8V3xFgAk/I69M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mXnuj7tDYLpwITlIhgK2PIiNY4VyMZjIh2RQ4oCzGBo2HZHtx63Lfohu7WnlMt9wMjDq4G+m5OK37h4Fz+ETMjuvRCQxFjsiP6+K0XhOZJuCfkSjlshZuxqUvAmMz8VlYiz8TxAVapEZ6c+OaotWAnPKlkanP5+bcybOPHCsvRQ= 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=XONS9Vc9; arc=none smtp.client-ip=209.85.210.170 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="XONS9Vc9" Received: by mail-pf1-f170.google.com with SMTP id d2e1a72fcca58-736c1cf75e4so213982b3a.2 for ; Wed, 02 Apr 2025 16:20:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1743636056; x=1744240856; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=fBphlYcwU/1hlzR4oiaNvWz06PFPPjN1Tjq9YA7ayac=; b=XONS9Vc9K053KWZn2eeBGYfTM4zxS3v3RT/2BwYCwN8ZJVHD8u7cihw+YSRD2Xk9fz sbCv67+YxxPZS5DKV/vdVuSQWbMpInB50SZEwumKpg+cVG7ZeEobZv2J+1v9RMugr6wb cYWWILoIO1sVWmrwIYJgnhHutoAg+tLCry5iQAZ8dZK7iyP2AEsjXsT415ehLMpqWWLN FM4Ggh+0kuk0Mub3TgZJCK2JRkCmRyHFOW7G6NDHK1q7aCrgE6iUBKY5+tL9g18ojtSu fzovY/rpTpWi3hgg4mJhG8Vrnqdmq1L8Q6E8+gA+vJ2SyD2QyjtzMq1Lp0/yzXLxYkJe c9BQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1743636056; x=1744240856; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=fBphlYcwU/1hlzR4oiaNvWz06PFPPjN1Tjq9YA7ayac=; b=jegcR6oztrnwoZK7fcSLz8zToAwiI8EAjmRnmeRBVgugsykX6WbossaFn0If0TQEXf kEjLVEavtHxfxj4W5v8gA7EMQlYUrgxoV6SJQzKLSNsmEWQo5+9xqMIdOZpyW1r18sKX loKtyvTkC+3Ssq7qPKUh8DnQnc4Ecl3UITFnLSZsrCvW1lViUSwFvUvFoJjk3t2QPwoq wYyC/pvUIFzVrqxtIdOIlgo3c0wD2cmH5fqHbX8PInQUfwfxahVE+tBgnEpNvbO+9d76 pky0s7v3zR+OWTmYOvhQzjq9rXQvaz+MEPDPZ9FvHfpkp8TmYfVD2uqwh1bSp+sgVWrx se6Q== X-Gm-Message-State: AOJu0YxahhKCoIqaQOFjdvkvoYqKn2DqjaOayot+AlH0wVhJLpuCRiPK yPx5CoWsc0W45yi4l7qnnArG33iHdYWi5YlZpgZjF+oOxPMPGR0= X-Gm-Gg: ASbGncv+z4H4AWJ4axuc1lgjDYkvQRfwBrCHV59oVxVGpHkOLNn54nZ4aqsfM1peGzK mL6oPLBgM6ckb68ctJ5/nxwlTJQOHTxzBV4Iwpt565gVZFMT+OkRf0gd2MrhTa5cu46xtdgO5is 7N+pgfNiRKiypSmSsV04QWt+yqpECkvC4rUMBUW91tNscXi44TWfbJ1H3yXVzc3Ub8iFzIAwwcS qMoNJajG6vdcfm4o7hKjNH3VQv3i/AGaIkM52UEq4R9aBaieP6YNeuYvvflD+llC0pYCnC/VWcM w3Ze6SdX5a+5vzNH0BRQ9E37bCpRS4ROLUX8aQxtbl6C X-Google-Smtp-Source: AGHT+IG0crscIMfhtK1DXLDymrpTotz+gLhsDilMsg0wLfOzwhxSJOei3KzTF9LhJx7s3hKZieD6iQ== X-Received: by 2002:a05:6a00:9285:b0:736:4110:5579 with SMTP id d2e1a72fcca58-73980322513mr23587869b3a.2.1743636056027; Wed, 02 Apr 2025 16:20:56 -0700 (PDT) Received: from localhost ([2601:646:9e00:f56e:123b:cea3:439a:b3e3]) by smtp.gmail.com with UTF8SMTPSA id 41be03b00d2f7-af9bc2cfa87sm17120a12.6.2025.04.02.16.20.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Apr 2025 16:20:55 -0700 (PDT) Date: Wed, 2 Apr 2025 16:20:54 -0700 From: Stanislav Fomichev To: Cosmin Ratiu Cc: "netdev@vger.kernel.org" , "sdf@fomichev.me" , "edumazet@google.com" , "davem@davemloft.net" , "kuba@kernel.org" , "pabeni@redhat.com" Subject: Re: another netdev instance lock bug in ipv6_add_dev Message-ID: References: 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-Disposition: inline In-Reply-To: On 04/02, Cosmin Ratiu wrote: > Hi, > > Not sure if it's reported already, but I encountered a bug while > testing with the new locking scheme. > This is the call trace: > > [ 3454.975672] WARNING: CPU: 1 PID: 58237 at > ./include/net/netdev_lock.h:54 ipv6_add_dev+0x370/0x620 > [ 3455.008776] ? ipv6_add_dev+0x370/0x620 > [ 3455.010097] ipv6_find_idev+0x96/0xe0 > [ 3455.010725] addrconf_add_dev+0x1e/0xa0 > [ 3455.011382] addrconf_init_auto_addrs+0xb0/0x720 > [ 3455.013537] addrconf_notify+0x35f/0x8d0 > [ 3455.014214] notifier_call_chain+0x38/0xf0 > [ 3455.014903] netdev_state_change+0x65/0x90 > [ 3455.015586] linkwatch_do_dev+0x5a/0x70 > [ 3455.016238] rtnl_getlink+0x241/0x3e0 > [ 3455.019046] rtnetlink_rcv_msg+0x177/0x5e0 > > The call chain is rtnl_getlink -> linkwatch_sync_dev -> > linkwatch_do_dev -> netdev_state_change -> ... > > Nothing on this path acquires the netdev lock, resulting in a warning. > Perhaps rtnl_getlink should acquire it, in addition to the RTNL already > held by rtnetlink_rcv_msg? > > The same thing can be seen from the regular linkwatch wq: > > [ 3456.637014] WARNING: CPU: 16 PID: 83257 at > ./include/net/netdev_lock.h:54 ipv6_add_dev+0x370/0x620 > [ 3456.655305] Call Trace: > [ 3456.655610] > [ 3456.655890] ? __warn+0x89/0x1b0 > [ 3456.656261] ? ipv6_add_dev+0x370/0x620 > [ 3456.660039] ipv6_find_idev+0x96/0xe0 > [ 3456.660445] addrconf_add_dev+0x1e/0xa0 > [ 3456.660861] addrconf_init_auto_addrs+0xb0/0x720 > [ 3456.661803] addrconf_notify+0x35f/0x8d0 > [ 3456.662236] notifier_call_chain+0x38/0xf0 > [ 3456.662676] netdev_state_change+0x65/0x90 > [ 3456.663112] linkwatch_do_dev+0x5a/0x70 > [ 3456.663529] __linkwatch_run_queue+0xeb/0x200 > [ 3456.663990] linkwatch_event+0x21/0x30 > [ 3456.664399] process_one_work+0x211/0x610 > [ 3456.664828] worker_thread+0x1cc/0x380 > [ 3456.665691] kthread+0xf4/0x210 > > In this case, __linkwatch_run_queue seems like a good place to grab a > device lock before calling linkwatch_do_dev. Thanks for the report! What about linkwatch_sync_dev in netdev_run_todo and carrier_show? Should probably also need to be wrapped? > The proposed patch is below, I'll let you reason through the > implications of calling NETDEV_CHANGE notifiers from linkwatch with the > instance lock, you have thought about this much longer than me. Yeah, I wonder whether other unlocked NETDEV_CHANGE paths can trigger a call to ipv6_add_dev. Will try to take a look. Initially I though that only NETDEV_UP will trigger ipv6_add_dev, but looks like it can happen on CHANGE as well :-(