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 EA00653D9CF; Thu, 15 Oct 2026 15:26:20 +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=1792077985; cv=none; b=SszpgaMDMzcV4gOcLJZ9rf7JuKDyReVgXYvIAz8vywWPFbGG4TdulqlQvU9TPD1YJJH9G6We1tqRiXNUuM3PENE33dkzK0ulaEOonSQHDKdIeE6Gl4musKA3NHXstOJHqyXS6jNNAuOmWzc1U/ph5oxQA5zi3lWO6kA6FG3/lEs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792077985; c=relaxed/simple; bh=lGFYszG+X9cD1RSaVXN6Cax+Ro7OIJYt6TuOEfxjm4U=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=ixQ+NQRjO/y53WfOBlK13wWEkjQ+7iENiz2ozj5MSrJ1rxcwEuTfuLMKaDFA67NeNQpj/o6YhCjcF1EvvBMsHvHCH44i8DLLq8aESnn0y9URYT/qKjYCYh+/+QSlFZaWkHpfAU8p8ql5UVVeAw+T3E09xZ2dDBvJR2Epz1U4VPs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KnjfDq1v; 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="KnjfDq1v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F18D1F000C4; Thu, 15 Oct 2026 15:26:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792077980; bh=atS3/rapI2FLFaIlwNm0Wvc9CuXO4ChyPjJlfJz6lcA=; h=Date:Subject:To:References:From:In-Reply-To; b=KnjfDq1vehw4BngSjPRpCcDX+AiEYUfHCML1u2RvRBw6Jhuzx3saJUw4Qgg75Vk+h ZXBATOsCX5lz1wNF6jUf0DXDDhHxbcE47eFX/rJarjh8fjxxmcHZo6yZllCypG0tIr /cqZhyh2suN1Ld/UILpDmsjhk+mwaY97j9BzVHi2avS2lZNt+BWmCaG7/ycGsUjGF4 OV34vlYLe69GW8nUGd+7295xBTVpv1R5ozVi4N0f8K4sOZ4ENVSMz7aV8oG2jEenjk X27cuw7P+fu6nGx3r1YEKh82aebAljD6DdfUl88P9ph0Nv1DVyfUtaT4fkhwaKnNbC bYUnYyLIlb7xw== Message-ID: Date: Thu, 15 Oct 2026 17:26:18 +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-net] mptcp: disconnect: reset first subflow's local_id Content-Language: fr To: sashiko-reviews@lists.linux.dev, MPTCP Linux References: <20261015-mptcp-first-disco-id-reset-v1-1-6ae41e8f02c6@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 15/10/2026 16:05, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [Critical] mptcp: NULL pointer dereference in mptcp_disconnect() on unconnected socket > -- > > commit 79fba9c250462a2f6852b46cf0562a508bcae604 > Author: Matthieu Baerts (NGI0) > > mptcp: disconnect: reset first subflow's local_id > > This commit resets the local_id of the first subflow to 0 when disconnecting. > This ensures the value is correctly initialized if the subflow is reused > after a reconnect. > > Link: https://lore.kernel.org/179198834484.434549.4616694240552704738@kernel.org > >> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c >> --- a/net/mptcp/protocol.c >> +++ b/net/mptcp/protocol.c >> @@ -3654,6 +3654,7 @@ static int mptcp_disconnect(struct sock *sk, int flags) >> */ >> mptcp_do_fastclose(sk); >> mptcp_destroy_common(msk); >> + WRITE_ONCE(mptcp_subflow_ctx(msk->first)->local_id, 0); > > [Severity: Critical] > Does this code cause a NULL pointer dereference in mptcp_disconnect() on an > unconnected socket? > > If a user creates an MPTCP socket via socket(AF_MPTCP, SOCK_STREAM, 0), What? AF_MPTCP??? > msk->first is initially NULL. If the user then calls connect() with > AF_UNSPEC before any connection is made, the networking core handles > AF_UNSPEC by directly invoking the socket's disconnect handler, > mptcp_disconnect(). Arf, I forgot about this weird path... I checked with shutdown() (which is not allowed for unconnected sockets). I will add a check and add a packetdrill test for this. > At this point, msk->first is still NULL. Passing it to mptcp_subflow_ctx() > yields an invalid pointer, leading to an immediate page fault when local_id > is written. > >> >> /* The first subflow is already in TCP_CLOSE status, the following >> * can't overlap with a fallback anymore > Cheers, Matt -- Sponsored by the NGI0 Core fund.