From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DBD553EFD22 for ; Wed, 2 Sep 2026 10:20:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788344408; cv=none; b=I9fW6sB3WQuTNKxZEg8jjUVSCOf4fTLua0Ow39xnCOl3YTwVUBPo6F2Vh2uDLKcxzsj3uTCfrn2Jj/weXoTJyZC5OxhE4bXt2hiccQQ/uhv0OjiI3COwNUK80Qq+0IM+noscv9k4yFpWrGOgPyaH8VEK85/UQn1I9lWgaSCAbWA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788344408; c=relaxed/simple; bh=koNzZumTx+nEjgCFQcInNi6PsZeQF1QwnSUpNVUm26c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kM1AynKPeACblaOzOE3sXSIJOJUyU/5apuVMk5xnlBWf8ARaGhE7EiGzz5qhU4BRZMLJPytN0yAHnzaLhmLslxzGEIK8cU8WpAI20sqQ9Hgx9b1j/X+3Vic7sx4l3Sbsj26cIT69T8IOIZbunAtcs+RkGYirJ8Z+VTr+rktLMMk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=g4RUI5lq; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="g4RUI5lq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B39051F000E9; Wed, 2 Sep 2026 10:20:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788344406; bh=rodD/1Qzq/0xB46EVh1cuAxzF8N28qRzrkLehYfkQEQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=g4RUI5lq6Y0oTxlhKKlLRTQTibZoJrTTGa5Lz7kVC00bvPkNSkJm3+fXrRbvtMdow /UerH6Et0GNQHhvtER3+ihwz4zVe94nUGjqpIY9MJXCfiL3CrlXLEZ2JLQSkILCQCe rFFdfGVhUdoekF9kOiPfqqfsGTv/r845aIFn6hVTDr+UXpbgbubYyTu0QBNGeXSZVa bUCdKrkTWFCjyWlzyvHIrqNgaIlt3EWGAKp2O5ouGGYSYcVQz0SVNF84Pubk26ptO7 eoiGn3izx6NQbPIMn9dy1/6Wv4ZX+UB/3YCgolPTPNvv9CtK9y2MExN30w83oiPwlN JnoolD5NKTf9Q== Message-ID: <19934016-686b-45f1-91de-8ff29e5a7a06@kernel.org> Date: Wed, 2 Sep 2026 12:20:03 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH mptcp-next v3] mptcp: fix skb_ext leak in fallback mode Content-Language: fr To: Geliang Tang , mptcp@lists.linux.dev Cc: Geliang Tang References: <6e4266b0dc3eb7e68f0064e16fa9921f46b85319.1788338252.git.tanggeliang@kylinos.cn> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Geliang, On 02/09/2026 10:39, Geliang Tang wrote: > From: Geliang Tang > > In fallback mode, MPTCP sockets behave as plain TCP and should not allocate > SKB_EXT_MPTCP for transmitted skbs. The current code unconditionally > allocates the extension, causing memory leaks when skbs are freed without > releasing it. I'm surprised by this. Do you have kmemleak reports? Or is it linked to this issue? https://github.com/multipath-tcp/mptcp_net-next/issues/583 I'm asking because I would think that such issues would have been caught by kmemleak, plus the fix is quite invasive. > Fix by short-circuiting __mptcp_add_ext() in fallback mode and skipping all > DSS bookkeeping in mptcp_sendmsg_frag(). Also allow TCP coalescing when > mpext is NULL in fallback mode. > > This latent bug will be exposed once TLS ULP support is added to fallback > MPTCP sockets, as each sendmsg via the TLS path would leak one skb_ext > object. Do you mean this bug is only visible with the new feature? If yes, then no need to threat it as a fix. Then, I'm also wondering if this patch shouldn't be specific to this case: maybe less code should be modified to deal with fallback sockets once this happens? (I'm probably missing context to really help here) Cheers, Matt -- Sponsored by the NGI0 Core fund.