From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-1.mta0.migadu.com [91.218.175.1]) (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 AC1594A92C6 for ; Thu, 3 Sep 2026 13:14:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.1 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788441300; cv=none; b=a3olg7IKveqIS61MXHkIB3qZbgcOTFKVV65EHq6LjjF/zplt1bjKuC7lfvSEamw7Up2aqCsXHtwcEOtJB4OFu5RpYHy3NmvLVw4a51XPJpHGh450/yEM/FiBKInNz9/5Spo8nyDNbj7iRsUI7TYknH49EQuQTRpakmFG6LqJttg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788441300; c=relaxed/simple; bh=vlz1b+Csbnkwq1bxemxyXf7jitsTYAMetSCARlCcwyc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VtQ03yt9PfeOtUb0SjS4th5ioB+HePcp5YUS5sEz3R9JjXh7DP5T3GenFoF3Ib7RgNngxLOE9308ZIzHr6NABDOqPIi/3jKNgPsYq3Ws36fpwqX6WWTpYrdGyN2mQ0cuNlPurYQ0z4u3/fwzI2Ja9Mvl19G7iqdglJsnIcafWNc= 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=xqsFKVMb; arc=none smtp.client-ip=91.218.175.1 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="xqsFKVMb" 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=1788441272; v=1; x=1789046072; b=xqsFKVMbcWDBFBrJlICrHU/yvmNZQM5wSRX0qszaz5f/TFlwpyAo9klZmQywZn7kX5w4HSqA sgLkXTmBIU8Gl0x94J/ZzB0wn4fbcwiRVMfmou2tHZpcBNCdRIJ0O90ifdmDpzWNwhrKJKWnJYQ 7jkV99dNgcI7a5Ts2pMJ5alE= X-Envelope-To: mptcp@lists.linux.dev Received: by smtp.migadu.com with ESMTPS id 05258866f3f1d093; Thu, 03 Sep 2026 13:14:32 +0000 X-Mizu-Trace-ID: 05258866f3f1d093 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 v2 1/3] mptcp: pm: bound extra_subflows admission on userspace PM Date: Thu, 3 Sep 2026 21:14:14 +0800 Message-ID: <20260903131416.1112393-2-cui.tao@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260903131416.1112393-1-cui.tao@linux.dev> References: <20260903131416.1112393-1-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