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 2EC864AA1C3 for ; Wed, 2 Sep 2026 16:39:31 +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=1788367174; cv=none; b=G73ECvr4U3+ClpqV96Xsp4MRNFk+pSEbQwEa+dsPDB4H6zeVJ2jMdZ/MgJjOsqG1Bl9/fWSPQaFpIaluWFyonYTLiFlZVOxJ3FEhLsoRckoLJV7kl1w1x2VWQzhHm+3ibjgvSq/3jpLtWYFs0+KvjfvvHLEbvzqXU1Jq6kZlqjQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788367174; c=relaxed/simple; bh=IxH+TcPFr9sHL+530fEBm6z5qUloI3xUMLjzxQ/REZI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OXdzanSp72hxSpZIIOdVbfFW/F70LEghNSz+ia9MMqA5nWErosAO13hkILpu5/RuCETUZ7zKhzhBx8vAVOMsS1rkay9jnivZ6ec5jjQc/nUZiw2mlSAf12wKsgfbMqwtCezArfTKVzbqECQTJdwzfgzLZsEsWyO/hioDFn0lv8A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=otjR0lMt; 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="otjR0lMt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A407B1F000E9; Wed, 2 Sep 2026 16:39:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788367171; bh=7UF9//x9ZInEFdxEVRUB4TF7+NOCSl/CF1dEkXjiuZc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=otjR0lMt7do8vvOOekPt80z/mV7g4owGxRwx0D4Tr9DHofu0FuwW+Jy4M/aO6CNff T9LCjWy50k2Di3mVxQ5QjbqeaN+Qz5F2dPuhm+up0oAAQokASrcUvZrSUQG1W+wGGI XIHuV6o3cooNOviplhHwar/R8fh4YPSX3HqX5czyoncC4QJsKyfLY80ldCYtxfUa1b 4n3TTOJEn7SJtPVEKKV4Abwn6tttWxm7aH6o8cKQVSylgSxxXuWSMz3gVjcrGbqfME FdrD4hgauKILetJmFhtPkLWj5DMTErt5EsAfM4rJcWXL+wrmeEHdERqpLHkgc/P+2D v5RFxSB1NSTjQ== Message-ID: Date: Wed, 2 Sep 2026 18:39:27 +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 1/2] mptcp: pm: bound extra_subflows admission on userspace PM Content-Language: fr To: Tao Cui , mptcp@lists.linux.dev Cc: geliang@kernel.org, cuitao@kylinos.cn, Quanye Yang References: <20260831093206.689827-1-cui.tao@linux.dev> <20260831093206.689827-2-cui.tao@linux.dev> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Tao, + cc Quanye On 31/08/2026 11:32, Tao Cui wrote: > From: Tao Cui > > mptcp_pm_allow_new_subflow() increments the u8 extra_subflows counter > for every accepted MP_JOIN on sockets using the userspace PM, without > any limit. A peer establishing more than 255 live subflows wraps the > counter back to 0, which then makes the underflow guards warn on the > next subflow close, and permanently corrupts mptcpi_subflows_total > reported to userspace. > > Refuse new MP_JOINs once the counter has reached U8_MAX, so that it > cannot wrap anymore. > > Fixes: e99c1ca89071 ("mptcp: pm: add WARN_ON_ONCE guards on extra_subflows underflow") > Link: https://github.com/multipath-tcp/mptcp_net-next/issues/629 Do you have a GitHub account? Just to know if we can assign this task to you (or just leave a message in the comment section). > Signed-off-by: Tao Cui > --- > net/mptcp/pm.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c > index 8b68868255c5..3990f6775723 100644 > --- a/net/mptcp/pm.c > +++ b/net/mptcp/pm.c > @@ -562,10 +562,17 @@ bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk) > > if (mptcp_pm_is_userspace(msk)) { > if (mptcp_userspace_pm_active(msk)) { > + bool allow; "ret" could be re-used here. > + > + /* extra_subflows is a u8: don't let a peer wrap it > + * with more than U8_MAX accepted MP_JOINs > + */ I don't think this comment is needed, "< U8_MAX" is probably clear enough. > spin_lock_bh(&pm->lock); > - pm->extra_subflows++; > + allow = pm->extra_subflows < U8_MAX; > + if (allow) > + pm->extra_subflows++; > spin_unlock_bh(&pm->lock); > - return true; > + return allow; > } > return false; > } So, at the end, we can re-used the same version as Quanye. Would it be OK for both of you to have a Co-developed-by tag here? Cheers, Matt -- Sponsored by the NGI0 Core fund.