From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f42.google.com (mail-wr1-f42.google.com [209.85.221.42]) (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 C0E5B3988E3 for ; Mon, 12 Oct 2026 16:42:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.42 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791823343; cv=none; b=B8DP1kGNcYcbJlew0ogT4lbVFRdkZVovuOeR3SynYg6I3v8nX14C5xzRHjZM1nVQH7J/l3feEdYBFH8ZzSpEM38Z5WQZFPhtyUv8eZ4pTE0dsZtqOTtIegl0V/YvRTp7RbYrzRFs6NxPus8zQ/Ap4wEluQzeokW9NFvt89/piA4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791823343; c=relaxed/simple; bh=EXC48ns2jWgAZUb2XLn2yHi+H3UJwk46qcn+bKkeKxM=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=BMOLkQw11vH3aN+dvsInF7KojBMcS1XCauXaPBsvd8MDcqMdznqPMLsLBqHJc9j+npWR8ES7GrVwAOx5xo+KMsWCZ29Xrl4UOBy9pj91w5lGGmBmSSb7CWM18pfCWkTieuGhI6VtulWWB1e04FSZ2hUM3MpYmj17SoGO3zgIbAU= 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=Bj8ZEyF7; arc=none smtp.client-ip=209.85.221.42 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="Bj8ZEyF7" Received: by mail-wr1-f42.google.com with SMTP id ffacd0b85a97d-48bbb06f29bso166588f8f.3 for ; Mon, 12 Oct 2026 09:42:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1791823340; x=1792428140; darn=vger.kernel.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :content-type:mime-version:subject:date:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=DbH0x+1VGrxmmG/67GKpm0AlwDDsWm6hJsBQAAEfQEQ=; b=Bj8ZEyF7mlJrBzYLeQpdXMfcbdhO/zeAYnHsrwj3wFPp46ekmGdCF3CxZXonS1GgM5 NXZN54NTi/8KZupzxcialHuP7zDXpMafHwGI6q1qHjRu7XMyUeWRPtCqQYSKZzCEaEi2 tjJoTDe/EI3VqB0dG8mQdIfm9f4eqy9LI/kY7iz+jWp19vQUEG7saVQzbA0cw82ICW8Q dJvwAinHrLB6YB9TV5bxDXe59vn3fZtZai+GzDUM+xpdUPifwAv7LcOUfVwpbCP3fuvf fThxrplRJtHcO40A1O19PiaSeVN+c6aYh3T2PXswW5qAB/5U+NFpu0YjPsUW1zggeffT vxuA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791823340; x=1792428140; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :content-type:mime-version:subject:date:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=DbH0x+1VGrxmmG/67GKpm0AlwDDsWm6hJsBQAAEfQEQ=; b=Oassg/J0avbpBOBedVYJyvGSPsxNOyMwFZ/9P+qFZWEACclU+k4GlBY6J67GQeHKMw J8K2OFc5un73hQYaZDF6auYZG/O4eBRWy4phukLy9Jx9eMl8SxrDnju60a+7e/qevfC/ dv0QLbsjouD8VjlDVXwBbKrLGli4kY+juPlroReFiXEtvr9sN/2RzyvPOsq3vaa7UviZ 82pDSzpCVK1ynAF4nOYPd6xMGIhRFd5ILfrttNAX5ANWzfEhkhLh9v/uyd9rcpV/f4QY blNZnNRiU6abhPYZ4E7y5qEydc0uXjWdRpde4i4EAB9xA1W92b8rF0xJdBlikUIoywjX t87Q== X-Forwarded-Encrypted: i=1; AKwUvByswH16TNYbKP96fShMmOvobRyA9J4SjM5e1fUPNw7bMCzvyHNA1T4urKnvZwAMvbK3KP4eJncFS7Omh1I=@vger.kernel.org X-Gm-Message-State: AFq9FYJtgVkI0PKCWsreEYWisj0m6/pUxAKgtg0nb0DFPrkYRVMOg6yd +V57FNVA4b0GQjJDeRP4TRunjkBuuQyKIQ66r6KX10SsD8y57mAOSedM X-Gm-Gg: AYBFou2p70yeJg9yRV6Yxh43K/uVkzOH4uzG9o1PnFFIJEFFblhvoBepdX5M7SglhE2 ptKhJmL+I0puKc6BowWqNaOH9M+SzXwJ0oUd+oPUxvA2fFbhLbtCxbXFkKAWtsEWQRi3OMj8FWA XARJ3BBHT/CU5ruKwZANhL0kOrT+Jo0ua2hgR/39KwYie/Zv3r1vCYPGojfVmOHNMO3mVo9Y2AH 5jCl6Qs13okxoh/j8p/Jc/kze1+9xbAUP+1cX2XqaSkz1OSzMN36CaOIiaduO34LEtuxTSPjJfr G/S4PttxpTL5XsroaZUTKebSjWlLSyG0uYYui3VVecU3eU8kCvVq2DTWpxqdbZGP7cpyM4N2WCw 58qjQhu+44EZQyrdzUM1Fxbk4o11iBTDaY9ZzIUBGQvCfAKEo5gLw/y1xmkkm9NP+JHSmYQyBzu Zbo3cxWHYdPIdaz14mX0wcNf/MAdjSPkpjrYHfUhFIsyoVkHNoLC/p86bTpifgmHg= X-Received: by 2002:a05:6000:4694:b0:48a:f4c1:4301 with SMTP id ffacd0b85a97d-48ddfb1b623mr910781f8f.6.1791823339056; Mon, 12 Oct 2026 09:42:19 -0700 (PDT) Received: from localhost ([2620:10d:c092:500::4:c555]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48de0967c03sm394228f8f.6.2026.10.12.09.42.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Oct 2026 09:42:18 -0700 (PDT) From: Gustavo Luiz Duarte Date: Mon, 12 Oct 2026 17:41:57 +0100 Subject: [PATCH net v3 1/2] netconsole: finish enabling the target before releasing RTNL Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261012-netcons-fixes-v3-1-1aac85ed7665@gmail.com> References: <20261012-netcons-fixes-v3-0-1aac85ed7665@gmail.com> In-Reply-To: <20261012-netcons-fixes-v3-0-1aac85ed7665@gmail.com> To: Breno Leitao , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Stephen Hemminger Cc: Gustavo Luiz Duarte , netdev@vger.kernel.org, linux-kernel@vger.kernel.org X-Mailer: b4 0.15.2 netcons_netpoll_setup() publishes nt->np.dev inside __netpoll_setup(), then releases the RTNL and waits for an RCU grace period before returning. Only after that does its caller store STATE_ENABLED. A NETDEV_UNREGISTER event landing in that window tears the target down and we end up storing STATE_ENABLED with a NULL np->dev, leading to a null-ptr-deref in netconsole_write(): BUG: KASAN: null-ptr-deref in netconsole_write+0xb9/0x7f0 Read of size 8 at addr 00000000000000a8 by task pr/netcon_ext0/135 netconsole_write+0xb9/0x7f0 nbcon_emit_next_record+0x501/0x550 nbcon_emit_one+0x10e/0x170 nbcon_kthread_func+0x2ff/0x3b0 kthread+0x199/0x1e0 Store STATE_ENABLED before dropping the RTNL lock to avoid racing with netconsole_netdev_event(). Fixes: 2382b15bcc39 ("netconsole: take care of NETDEV_UNREGISTER event") Signed-off-by: Gustavo Luiz Duarte --- drivers/net/netconsole.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index b358e5c36735..1fb846ad07d1 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -552,13 +552,16 @@ static int netcons_netpoll_setup(struct netconsole_target *nt) err = __netpoll_setup(np, ndev); if (err) goto put; - rtnl_unlock(); /* Make sure all NAPI polls which started before dev->npinfo * was visible have exited before we start calling NAPI poll. * NAPI skips locking if dev->npinfo is NULL. + * Hold RTNL until enable is finished so we don't race with + * netconsole_netdev_event() */ - synchronize_rcu(); + synchronize_net(); + nt->state = STATE_ENABLED; + rtnl_unlock(); return 0; @@ -589,7 +592,6 @@ static void resume_target(struct netconsole_target *nt) return; } - nt->state = STATE_ENABLED; pr_info("network logging resumed on interface %s\n", nt->np.dev_name); } @@ -1067,7 +1069,6 @@ static ssize_t enabled_store(struct config_item *item, goto out_unlock; } - nt->state = STATE_ENABLED; pr_info("network logging started\n"); } else { /* false */ /* We need to disable the netconsole before cleaning it up @@ -2669,8 +2670,6 @@ static struct netconsole_target *alloc_param_target(char *target_config, * otherwise, keep the target in the list, but disabled. */ goto fail; - } else { - nt->state = STATE_ENABLED; } populate_configfs_item(nt, cmdline_count); -- 2.56.0