From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f44.google.com (mail-ej1-f44.google.com [209.85.218.44]) (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 735963B775C for ; Thu, 12 Mar 2026 09:37:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773308265; cv=none; b=SrPu5PINGSTlYqTyQkBP4EGxpC7s6C3TUocdu+9oZNORFsoK5ke1fDZQl+oeEK1dvgr0QODZ5KmqKJjfvNXHaBUXj9mUH7FsmUf0nL41uro2KIxQkRzHxesXX/Dgk3Zm/LwQVuZNsIEY3aFCdwV0Yo4iz9tn3kMk6BdccIEabnw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773308265; c=relaxed/simple; bh=nmS+lsmzgEPjEn3riI1mvL7c2Eoou0UuR1cS2D2z6U4=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=C0qAv9VwFquJTnVSVB4sdd5T3J6cDGylp4iCm6giKrzWGrz6Rc38QbMaDsQhnxNlPien/sDsrHJqd+U04xU/xPKH4CgimbSWtN3Qomles+6ihDGFR1qgViZZrTsooXvL1zn3MNuZHs68MOGCPtlkUmSl041n/NhikDnzZG0soTU= 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=Fkc7Kz06; arc=none smtp.client-ip=209.85.218.44 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="Fkc7Kz06" Received: by mail-ej1-f44.google.com with SMTP id a640c23a62f3a-b942424d231so93067866b.0 for ; Thu, 12 Mar 2026 02:37:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1773308260; x=1773913060; 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=OMylDifb+sgwUdyQ3doSis8cOmZPRv2aLJLRsCDWhws=; b=Fkc7Kz06QLN/zyyVNUx84VpZu3Wefio2PbXKknTvreAJwVTi0A0GG78OEMONAeUHhr Ygn+LRAEeRvixuubkQ7L/avK4ptZG1455jBA9ZnpkdIub1cV0wSl/QjyK8io0zrP/ykz QYazmzU8AVxkEGNNNcWmdHN1CGK2euardpaC/o+PZopf42M7dFKzdvjPHhOrnaa3S+CT PbyNYo+bYqLiffRSDo9EZhE9AZx/wKx6Ywt86/QncB8pAzfU4RJ1mLL+q1kGtjJ0yk5Y ISxBn+duKirsLg22BKIeyW3YpQwGyDEtM9Ui8U6Oici9ZuebcHizFRl4FxkpFBxmvCLm AQ+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773308260; x=1773913060; h=content-transfer-encoding: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; bh=OMylDifb+sgwUdyQ3doSis8cOmZPRv2aLJLRsCDWhws=; b=YfovO4+AR5QvLvR2Pv5KFGpkIsuvp4vmsj3mLLAceTM8biTgoLeMt/dsDVIKxFE2Fr gr5LPNtsQnuPcik7Et9oE7J1LY4id0PIU60To24omYJwQIllRIGbPXDSJc9OAOV9bmNa yh3wE6htuCADLgEVMbQY8sVmYY2YSAnq+9wTpwu0UXvd0kOrCc8leFEiHSMuE1P2braU /c9j9OAmHnl4RKrcNVS/JUi0PoxTG0doopuCuG6JiLlb8uDMPN2hDjUY9PdbMuDNVStx UJsVzzMwQgq7nYdxiwprBNkvhmdPhmgZmKuiMfMxf5T5xz+xInGgPDIX7ZhToxvwRa6c wKSQ== X-Forwarded-Encrypted: i=1; AJvYcCV6V81+rHfG5F//xDzc2diwQLYfNQ1YhTcIZyIsoCgGKDdPZwP9XRRmFs/lasFyr/ognZW+l60=@vger.kernel.org X-Gm-Message-State: AOJu0Yz5ukPdhnzGuMMbgFKQWsZ47oUH80j9JZSdburAFSwaOFwuiyXT ojSZcqi2oM1IlpFdDrusd/SMkE/E3ogj2ZM8ie6MLa+9sfyWEAlhGDkq X-Gm-Gg: ATEYQzxbP8cjZ8VSqFXaHZ4An3cISfdEG5fvlJ3bOE/K8gLes/k0J5BEhMq1P57LgG8 VIhBdlcEXihbSeCE6lWzjp8CprVSd+qWpy/7cC/k5foOsA6cMre9cLxPfC7moF5P84wZ1LScZcE 77e0RlOtfSLuve2uBG/7TEsVxYFVke5Td2K/Re3d/a24DRpwIdZvXQhIhDvfIu8eHIvLdcHrxpE taFib4kSDp8h9rapIq9ZU52FQn6Bd6XIQWZlKnee1NlQ3cqLDp51BILGHpu0IT2JUuZoE+4geoQ FAppG/R2i+eXpl3HMY6/cqfTpIJ+hddnOYwoslCEKhqTFbLdyYaQzgFes6sqMQHkAIrM5EfABj7 oVPR2+4vxoY9T5dJ7Kl7qvPi5yB2fGI4icpqinf5DjZcjpeWkRSCvLiL2PT1uTS+hOAMN4Frg X-Received: by 2002:a17:907:9452:b0:b93:8995:8f3a with SMTP id a640c23a62f3a-b972e1ac726mr317393666b.3.1773308259284; Thu, 12 Mar 2026 02:37:39 -0700 (PDT) Received: from gmail.com ([2a09:bac1:5560::49b:47]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b972de82bc0sm114022666b.27.2026.03.12.02.37.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2026 02:37:38 -0700 (PDT) From: Qingfang Deng To: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-ppp@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Paul Mackerras Subject: [PATCH net-next 1/2] ppp: disconnect channel before nullifying pch->chan Date: Thu, 12 Mar 2026 17:37:30 +0800 Message-ID: <20260312093732.277254-1-dqfext@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In ppp_unregister_channel(), pch->chan is set to NULL before calling ppp_disconnect_channel(), which removes the channel from ppp->channels list using list_del_rcu() + synchronize_net(). This creates an intermediate state where the channel is still connected (on the list) but already unregistered (pch->chan == NULL). Call ppp_disconnect_channel() before setting pch->chan to NULL. After the synchronize_net(), no new reader on the transmit path will hold a reference to the channel from the list. This eliminates the problematic state, and prepares for removing the pch->chan NULL checks from the transmit path in a subsequent patch. Signed-off-by: Qingfang Deng --- drivers/net/ppp/ppp_generic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 6344c5eb0f98..ad480b584e25 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -3032,12 +3032,12 @@ ppp_unregister_channel(struct ppp_channel *chan) * This ensures that we have returned from any calls into * the channel's start_xmit or ioctl routine before we proceed. */ + ppp_disconnect_channel(pch); down_write(&pch->chan_sem); spin_lock_bh(&pch->downl); WRITE_ONCE(pch->chan, NULL); spin_unlock_bh(&pch->downl); up_write(&pch->chan_sem); - ppp_disconnect_channel(pch); pn = ppp_pernet(pch->chan_net); spin_lock_bh(&pn->all_channels_lock); -- 2.43.0