From nobody Sat Sep 5 05:48:58 2026 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: quoted-printable Content-Type: text/plain; charset="utf-8" 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 =3D pm->extra_subflows < U8_MAX; + if (ret) + pm->extra_subflows++; spin_unlock_bh(&pm->lock); - return true; + return ret; } return false; } --=20 2.43.0 From nobody Sat Sep 5 05:48:58 2026 Received: from mta1.migadu.com (out-19.mta1.migadu.com [95.215.58.19]) (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 0D4834ACC8D for ; Thu, 3 Sep 2026 13:14:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.19 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788441313; cv=none; b=fIC0FynN+WB+SBWVNqfByWG1KJfnmBRzrEeFvn3A09FmGDYMbZhLhkYAWR1JZ4oZYWpgStWpjCJzdoaXq8Am1xchWcdRvHiHCYQ/OX/abK6AXaSIqo/tNP+UcuaiJ3kKBSwtUhqbsSfAdvoRKN3iE5AhSh1utc6iciRJs1Se/Vg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788441313; c=relaxed/simple; bh=2nuUgjgidPHLBNI2V9fz+MDWuBGphq9N7I7kryTPoKU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=t559JZfb+/u4ujc//RYpjbqdBBnxlAryQC8WUz8WjNeBGcHM4d91A/Auxv1exFy/DtPDMLJe6VmQD4N+TdUOOZ/fiztxZIfumVofmtWCIQnYmBnGuXOxMdOPA1EXDCrxsBgMxKbAt1LKoXXT5MJV7KXMWJRBbh/n3xYPdUap+d4= 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=pYPFBHUG; arc=none smtp.client-ip=95.215.58.19 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="pYPFBHUG" X-Envelope-To: mptcp@lists.linux.dev DKIM-Signature: a=rsa-sha256; bh=2nuUgjgidPHLBNI2V9fz+MDWuBGphq9N7I7kryTPoKU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788441274; v=1; x=1789046074; b=pYPFBHUG8E5fpQ6cLcka8N8g6vjCinCwiB4LYN7dgK7R3JJNL0S7PCpbo1mLKkh6HIqLZCbL q07KFUbwMluLpMZFRLwxk4x8EVUygMKA0Gfpmw4nYumJ3qhyrO/OdVQtzip+UNbRiFCsnPfarYZ IuLfgCJvw4wbWYSXGFR+j0Rg= X-Envelope-To: mptcp@lists.linux.dev Received: by smtp.migadu.com with ESMTPS id 6532a9406f735565; Thu, 03 Sep 2026 13:14:34 +0000 X-Mizu-Trace-ID: 6532a9406f735565 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 2/3] mptcp: pm: skip extra_subflows accounting on disconnected msk Date: Thu, 3 Sep 2026 21:14:15 +0800 Message-ID: <20260903131416.1112393-3-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: quoted-printable Content-Type: text/plain; charset="utf-8" From: Tao Cui The WARN_ON_ONCE() guards added to the extra_subflows decrement sites turn out to be reachable: mptcp_pm_data_reset() zeroes the counter with only the msk socket lock held, while an MP_JOIN subflow can still sit in msk->join_list, its reference already accounted by mptcp_pm_allow_new_subflow() under pm->lock. If the socket gets disconnected(AF_UNSPEC) in that window, mptcp_pm_data_reset() zeroes the counter, and the join list is flushed later at release_sock() time: the leftover subflow then reaches mptcp_pm_subflow_check_next() (or __mptcp_pm_close_subflow() for kernel PM sockets) with the counter already at 0, firing the warning. On panic_on_warn kernels this is a remotely triggerable panic, which is worse than the silent wrap the guards replaced. Skip the PM accounting when the msk is already in TCP_CLOSE: in the scenario above the state is set before the counters are cleared, and once the msk is closed the accounting is not relevant anymore. Keep a clamp and a rate-limited pr_warn() on the decrement sites instead, to leave a trace of any imbalance we would still not know about. Fixes: e99c1ca89071 ("mptcp: pm: add WARN_ON_ONCE guards on extra_subflows = underflow") Link: https://github.com/multipath-tcp/mptcp_net-next/issues/629 Suggested-by: Matthieu Baerts Signed-off-by: Tao Cui --- net/mptcp/pm.c | 11 ++++++++++- net/mptcp/protocol.h | 14 ++++++++++++-- 2 files changed, 22 insertions(+), 3 deletions(-) diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 07cdcdb54b15..cccf5319cce0 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -671,9 +671,18 @@ void mptcp_pm_subflow_check_next(struct mptcp_sock *ms= k, update_subflows =3D subflow->request_join || subflow->mp_join; if (mptcp_pm_is_userspace(msk)) { if (update_subflows) { + /* The PM counters have already been cleared if the + * msk got disconnected while this subflow was still + * queued in the join list + */ + if (inet_sk_state_load(sk) =3D=3D TCP_CLOSE) + return; spin_lock_bh(&pm->lock); - if (!WARN_ON_ONCE(pm->extra_subflows =3D=3D 0)) + if (likely(pm->extra_subflows)) pm->extra_subflows--; + else + pr_warn_ratelimited("extra_subflows underflow, msk=3D%p\n", + msk); spin_unlock_bh(&pm->lock); } return; diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 87ccb84e9927..07821551499c 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -1252,8 +1252,18 @@ u8 mptcp_pm_get_limit_extra_subflows(const struct mp= tcp_sock *msk); /* called under PM lock */ static inline void __mptcp_pm_close_subflow(struct mptcp_sock *msk) { - if (!WARN_ON_ONCE(msk->pm.extra_subflows =3D=3D 0) && - --msk->pm.extra_subflows < mptcp_pm_get_limit_extra_subflows(msk)) + /* The PM counters have already been cleared if the msk got + * disconnected while this subflow was still queued in the + * join list + */ + if (inet_sk_state_load((struct sock *)msk) =3D=3D TCP_CLOSE) + return; + + if (unlikely(msk->pm.extra_subflows =3D=3D 0)) { + pr_warn_ratelimited("extra_subflows underflow, msk=3D%p\n", msk); + return; + } + if (--msk->pm.extra_subflows < mptcp_pm_get_limit_extra_subflows(msk)) WRITE_ONCE(msk->pm.accept_subflow, true); } =20 --=20 2.43.0 From nobody Sat Sep 5 05:48:58 2026 Received: from mta0.migadu.com (out-7.mta0.migadu.com [91.218.175.7]) (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 6442F4A5C5C for ; 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arc=none smtp.client-ip=91.218.175.7 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="X1qXMeXw" X-Envelope-To: mptcp@lists.linux.dev DKIM-Signature: a=rsa-sha256; bh=dQC+vnNQC+XmcfKQspZclbWnmxlFV57/2KbkmRdIpiI=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788441277; v=1; x=1789046077; b=X1qXMeXwwycQOMac/DCgojhGcId721bB+VuEwne47I6UpNPvTLE0X4XhhC6C0kXnVmsXkaan KK1h7J5bw/3j7CZnSdKJH5GYMT7j2SW+/tKQP+fkG+X4zgIf4/NeIHEELHGEmQevrYLqNbCNw/7 knWHyd8a6l92DQjSzXH4YY0M= X-Envelope-To: mptcp@lists.linux.dev Received: by smtp.migadu.com with ESMTPS id 4766c63bffb36d6c; Thu, 03 Sep 2026 13:14:37 +0000 X-Mizu-Trace-ID: 4766c63bffb36d6c 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 3/3] mptcp: pm: userspace: cap extra_subflows on Netlink subflow creation Date: Thu, 3 Sep 2026 21:14:16 +0800 Message-ID: <20260903131416.1112393-4-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: quoted-printable Content-Type: text/plain; charset="utf-8" From: Quanye Yang 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. Refuse the subflow creation with -ENOSPC once the counter has reached U8_MAX, and clean up the local address entry in that case as well. Fixes: 77e4b94a3de6 ("mptcp: update userspace pm infos") Link: https://lore.kernel.org/all/20260902-mptcp-pm-extra-subflows-v1-1-685= 40a866e5a@proton.me/ Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/629 Signed-off-by: Quanye Yang Signed-off-by: Tao Cui --- net/mptcp/pm_userspace.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c index b94fbb483bf9..3371e17d01b9 100644 --- a/net/mptcp/pm_userspace.c +++ b/net/mptcp/pm_userspace.c @@ -417,6 +417,12 @@ int mptcp_pm_nl_subflow_create_doit(struct sk_buff *sk= b, struct genl_info *info) local.ifindex =3D entry.ifindex; =20 spin_lock_bh(&msk->pm.lock); + if (msk->pm.extra_subflows =3D=3D U8_MAX) { + spin_unlock_bh(&msk->pm.lock); + GENL_SET_ERR_MSG(info, "too many extra subflows"); + err =3D -ENOSPC; + goto delete_addr; + } msk->pm.extra_subflows++; spin_unlock_bh(&msk->pm.lock); =20 @@ -424,9 +430,11 @@ int mptcp_pm_nl_subflow_create_doit(struct sk_buff *sk= b, struct genl_info *info) err =3D __mptcp_subflow_connect(sk, &local, &addr_r); release_sock(sk); =20 - if (err) { + if (err) GENL_SET_ERR_MSG_FMT(info, "connect error: %d", err); =20 +delete_addr: + if (err) { spin_lock_bh(&msk->pm.lock); mptcp_userspace_pm_delete_local_addr(msk, &entry); spin_unlock_bh(&msk->pm.lock); --=20 2.43.0