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 5C7E74B2CBE; Thu, 3 Sep 2026 14:08:21 +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=1788444510; cv=none; b=Op8VuLz3nCGqtsXS18s8APwz8j3ngZky2c3rxPXoNIHrL+hyJrfYxYhSMwCzFH75+X/E9vQUh54yYQ4kryLfESCPZQEGzwPgd3LCB/n96Fu5c6xJz4nlwSdRzuGNHnHrQopd6XP9e9fveaFcCz3Y6Rqq9/Ebx/rnVs+zGvheiJk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788444510; c=relaxed/simple; bh=HqtucKQs69uqiusNuysC+GtgjKkDe2ZAuZ41UEfxXLg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LFyuiKwBVLFJoGEZLOeyOHKFCgrrYTpcMeLmxKOLWA2c3CaiaWJoVytWHYr9v2E/RMWtFnNTiU+hI5dnT2o+VSy1tPlfZnuQALcHGs4wyhv1HARPFdS+/GVDeRZzRIwA6hszeLA5VeKODVvtAcsg56/JvEvNH4EV3+EzDOlFQXc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WCRSsA/G; 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="WCRSsA/G" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 149A31F00A3D; Thu, 3 Sep 2026 14:08:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788444498; bh=bswW5OkwpdCoGKq55o4iM/KzpAShp90fQkCwndVvvQY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=WCRSsA/G8YhL+bb0udQ0zge7fD/f+NDTV6TYfQ4+StIogIK+JIYmiOtRyjTaDxgRF rLZjtoXIZ6c1CwT/DwdCWW5fna2j9IYBaq96YjvoDHjlhg2IW+YHnx2sfzkke54RSv h36hQ9G4CRQTDbLB1uFn05RAZv4Xj57oCE8eeW3WaH06q/SeHeI7phyB9pJrUbrScH tEyXmBvSDYiej3KrxNuuBDt+1ZwTRwV0IyFT05yk3VnJBI/EBzrgOSyfHmZy34mzyi 6KzkOmwCb1bSNRtwpbAgm/BlJUax/2TuqqSsXd4C7mKAgixmrahM/Bwbql18zd+TTF D/RUKOuoNfpmg== Message-ID: <37501367-99e7-4ce0-a590-b8d5c1f9be0e@kernel.org> Date: Thu, 3 Sep 2026 16:08:16 +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 v2 3/3] mptcp: pm: userspace: cap extra_subflows on Netlink subflow creation Content-Language: fr To: sashiko-reviews@lists.linux.dev, Tao Cui Cc: mptcp@lists.linux.dev References: <20260903131416.1112393-1-cui.tao@linux.dev> <20260903131416.1112393-4-cui.tao@linux.dev> <20260903132757.5A7C11F000E9@smtp.kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hello, On 03/09/2026 15:27, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > > Pre-existing issues: > - [High] This problem wasn't introduced by this patch, but the error path unconditionally deletes and frees a local address entry, even if the address was pre-existing and shared among multiple subflows. > -- > > commit 147f86e2aec9bdeead6dcc987672ad229b2286ec > Author: Quanye Yang > > mptcp: pm: userspace: cap extra_subflows on Netlink subflow creation > > mptcp_pm_nl_subflow_create_doit() also increments the u8 extra_subflows > counter without any limit: a client with CAP_NET_ADMIN can create more > than 255 extra subflows via Netlink and wrap the counter back to 0, > with the same effects as the MP_JOIN path now bounded separately: > the underflow guards warn on the next subflow close, and > mptcpi_subflows_total reported to userspace is corrupted. > > Link: https://lore.kernel.org/all/20260902-mptcp-pm-extra-subflows-v1-1-68540a866e5a@proton.me/ > >> diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c >> index f723a134356f3..bede75a2e2586 100644 >> --- a/net/mptcp/pm_userspace.c >> +++ b/net/mptcp/pm_userspace.c >> @@ -427,6 +427,12 @@ int mptcp_pm_nl_subflow_create_doit(struct sk_buff *skb, struct genl_info *info) >> local.ifindex = entry.ifindex; >> >> spin_lock_bh(&msk->pm.lock); >> + if (msk->pm.extra_subflows == U8_MAX) { >> + spin_unlock_bh(&msk->pm.lock); >> + GENL_SET_ERR_MSG(info, "too many extra subflows"); >> + err = -ENOSPC; >> + goto delete_addr; >> + } >> msk->pm.extra_subflows++; >> spin_unlock_bh(&msk->pm.lock); >> >> @@ -434,9 +440,11 @@ int mptcp_pm_nl_subflow_create_doit(struct sk_buff *skb, struct genl_info *info) >> err = __mptcp_subflow_connect(sk, &local, &addr_r); >> release_sock(sk); >> >> - if (err) { >> + if (err) >> GENL_SET_ERR_MSG_FMT(info, "connect error: %d", err); >> >> +delete_addr: >> + if (err) { >> spin_lock_bh(&msk->pm.lock); >> mptcp_userspace_pm_delete_local_addr(msk, &entry); > > [Severity: High] > This is a pre-existing issue, but does this error path incorrectly delete a > shared local address entry if the address was pre-existing? > > When mptcp_userspace_pm_append_new_local_addr() is called earlier in > mptcp_pm_nl_subflow_create_doit(), it might match an already existing local > address instead of appending a new one. > > If the newly added extra_subflows limit is hit (or if > __mptcp_subflow_connect() fails), the code jumps to this delete_addr error > path. > > Because mptcp_userspace_pm_append_new_local_addr() did not allocate a new > entry but simply reused the existing one, unconditionally calling > mptcp_userspace_pm_delete_local_addr() prematurely frees the shared address > and decrements the local_addr_used counter, potentially corrupting the state > for other subflows relying on it. Correct, but there are pending patches from Geliang fixing that. Cheers, Matt -- Sponsored by the NGI0 Core fund.