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 27D4F331EAB; Tue, 16 Jun 2026 16:39:15 +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=1781627956; cv=none; b=nftrkS9D7ZXGHZORqG17wwu9JwCEvr/q4p7HFZ6bOgbls/CmMgrpBVTdSWHNrSapyEd95GckSAra/JuxToFk/LqDqWglS4cQUv+SPmiWrZJjJem1cr6GiERX21vPcy6N5YpkgeJBCRTrqqPda7Xz3KrX9AKn3i2ejSGR325TVSs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781627956; c=relaxed/simple; bh=lPWxdJq5sOnoeQtFB8ELMFqnGaCmmlTeJXelN4WNjzo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pE4NOepbzNPhjgc1uCB5ySfCDSWOmFFFuNHywkKYfffqj3XnmY6+SB50UfTwjWXYJV2ooxd0fTAz22OvAU/7wRSk4EWG1doYmVmInzWrPvGVouH5+uHTByKsN/KyX9A6w1jow4ilVsn/V7csNgvwaRMlQ9OrQcJ2u64SP625J1w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=x/aPOgFh; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="x/aPOgFh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 194BC1F000E9; Tue, 16 Jun 2026 16:39:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781627955; bh=itphzukPATok8/UWOhL2pqaHXapcefBq1M7xaNbEUWM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=x/aPOgFhcy1IskroC0BOyuiXMJP5/Qrt5+fF0jaJ9YR06NHR+64xD4wNvLFcQt/CJ E3V9eXQ99++rP2sLa+1bWh0jk8LSWJTCCabi14IVxou1v4xyNPs1Y/HpMQg4aL79aA rkcuvdZr9vNxcZjc8gW8U8+zDTyyg+BUEVmZZzhA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tao Cui , "Matthieu Baerts (NGI0)" , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.12 260/261] mptcp: pm: fix extra_subflows underflow on userspace PM subflow creation Date: Tue, 16 Jun 2026 20:31:38 +0530 Message-ID: <20260616145057.111743938@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145044.869532709@linuxfoundation.org> References: <20260616145044.869532709@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tao Cui commit 14e9fea30b68fc75b2b3d97396a7e6adb544bd2a upstream. The userspace PM increments extra_subflows after __mptcp_subflow_connect() succeeds, but __mptcp_subflow_connect() calls mptcp_pm_close_subflow() on failure to roll back the pre-increment done by the kernel PM's fill_*() helpers. Because the userspace PM hasn't incremented yet at that point, this decrement is spurious and causes extra_subflows to underflow. Fix it by aligning the userspace PM with the kernel PM: increment extra_subflows before calling __mptcp_subflow_connect(), so the existing error path in subflow.c correctly rolls it back on failure. Also simplify the error handling by taking pm.lock only when needed for cleanup. Fixes: 77e4b94a3de6 ("mptcp: update userspace pm infos") Cc: stable@vger.kernel.org Signed-off-by: Tao Cui Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260602-net-mptcp-misc-fixes-7-1-rc7-v2-5-856831229976@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- net/mptcp/pm_userspace.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) --- a/net/mptcp/pm_userspace.c +++ b/net/mptcp/pm_userspace.c @@ -402,16 +402,19 @@ int mptcp_pm_nl_subflow_create_doit(stru local.flags = entry.flags; local.ifindex = entry.ifindex; + spin_lock_bh(&msk->pm.lock); + msk->pm.subflows++; + spin_unlock_bh(&msk->pm.lock); + lock_sock(sk); err = __mptcp_subflow_connect(sk, &local, &addr_r); release_sock(sk); - spin_lock_bh(&msk->pm.lock); - if (err) + if (err) { + spin_lock_bh(&msk->pm.lock); mptcp_userspace_pm_delete_local_addr(msk, &entry); - else - msk->pm.subflows++; - spin_unlock_bh(&msk->pm.lock); + spin_unlock_bh(&msk->pm.lock); + } create_err: sock_put(sk);