From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-253.mta0.migadu.com [91.218.175.253]) (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 986D240F75A for ; Fri, 4 Sep 2026 05:12:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.253 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788498731; cv=none; b=cGtyowwDzVGlHTBnPDxNGEnYoTeZocBOSpTMI4c0+S4791yjrqodgZIJs0HJ0A3kC1sj0P4I7Z3T0NEQN8oNc5rGVqSgvbtMEdRQaYAfhJnAgyieA8snwRtKIhLexAa+vG1LjpAfgsFE8ZhZkFX0L6k8TohUfvpaERkG6MWSATY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788498731; c=relaxed/simple; bh=vlz1b+Csbnkwq1bxemxyXf7jitsTYAMetSCARlCcwyc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=P0AMT6wqDhnI9lYPci/LiLQJ3qFQuOXyqjtPuHhDihsZQymaF4ATNnf3MbxMR2AkV0jMYWrerEEjjIzRkJdqqQFPrNp59fUI3o1Pq7T6IVcsPQ76ug+luTl1FXw80k/NQGp4mrORS0C6OcECuUwPe5pYevNfFu3FE38Lj7KEE8c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=g/+RuDyl; arc=none smtp.client-ip=91.218.175.253 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="g/+RuDyl" X-Envelope-To: mptcp@lists.linux.dev DKIM-Signature: a=rsa-sha256; bh=vlz1b+Csbnkwq1bxemxyXf7jitsTYAMetSCARlCcwyc=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788498727; v=1; x=1789103527; b=g/+RuDylHRxqn6fCiEyk+R1S91o1AxW3rFDOF1X41G7YCw4Zg6gYHYkxAuaThfmRY2guOSZT tRolH40jRGhZW92IzhFST4D+ryVstR904e/uxGDt3Yly3JFNZd3frpiBJHW33ndGuJJmdZfaoRG l/r7LNO1BIZ1rpcSk4Y0+vxo= X-Envelope-To: mptcp@lists.linux.dev Received: by smtp.migadu.com with ESMTPS id 9a802a4186d0bdfc; Fri, 04 Sep 2026 05:12:07 +0000 X-Mizu-Trace-ID: 9a802a4186d0bdfc X-Migadu-Flow: FLOW_OUT From: Tao Cui To: mptcp@lists.linux.dev, matttbe@kernel.org, quanyeyang@proton.me Cc: geliang@kernel.org, cuitao@kylinos.cn, cui.tao@linux.dev Subject: [PATCH mptcp-next v3 1/3] mptcp: pm: bound extra_subflows admission on userspace PM Date: Fri, 4 Sep 2026 13:11:48 +0800 Message-ID: <20260904051150.1196427-2-cui.tao@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260904051150.1196427-1-cui.tao@linux.dev> References: <20260904051150.1196427-1-cui.tao@linux.dev> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Co-developed-by: Quanye Yang Signed-off-by: Quanye Yang Signed-off-by: Tao Cui --- net/mptcp/pm.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 8b68868255c5..07cdcdb54b15 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -563,9 +563,11 @@ bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk) if (mptcp_pm_is_userspace(msk)) { if (mptcp_userspace_pm_active(msk)) { spin_lock_bh(&pm->lock); - pm->extra_subflows++; + ret = pm->extra_subflows < U8_MAX; + if (ret) + pm->extra_subflows++; spin_unlock_bh(&pm->lock); - return true; + return ret; } return false; } -- 2.43.0